Here in Canada, I believe the commissionaires would be the rough equivalents to China's 城管. Commissionaires are often former veterans and are hired to provide security at various government and civic sites.
While not exactly equivalent in terms of relationship to the government, there are some similarities. See:
http://www.commissionaires.ca/about/history.html

city officials or local tyrants.

Introduction
According to Decision of Beijing Municipal Government on Further Promoting the Work for the Relatively Centralized Power of Administrative Penalties on Municipality Management(Order No. 24 Promulgated by Beijing Municipal Government in 2002) and Circular of Office of Municipal Government on Printing and Distributing the Regulations on Function Disposition, Inner Divisions and Personnel of Beijing Municipal Bureau of Comprehensive Administration(Order No. 59 Promulgated by Beijing Municipal Government in 2002), the former Beijing Municipal Supervision Office is changed to be Beijing Municipal Law En-forcing Bureau of Comprehensive Administration, governed by Beijing Municipal Administration Commission, perform its official functions and promote its work in its own name.

link

The Chinese original of toold's link is available here. I'm not convinced that 北京市城市管理综合行政执法局 is best rendered as "Beijing Municipal Law-Enforcing Bureau of Comprehensive Administration," if only because the site doesn't follow its own translation policy: it calls itself "Beijing Municipal Law-Enforcing Bureau of City Comprehensive Administration."

I tend to prefer "municipal thug-bastards."

rent-a-cops

I asked myself exactly this question when I read this article in the Guardian last week: link

It called the chengguan “city officials” and, being familiar with the story, I thought “Hmm ‘officials’ that sounds, well… official. That word is normally short for ‘communist party officials’ who are carefully screened before selection (in theory) and who abide by strict rules (on occasion).

Chengguan are more like bully boys.

A few paragraphs later the journalist uses the word chengguan, which clears things up if you are familiar with the Chinese term.

I asked a few Chinese journalists and they weren’t too helpful. “Not sure” “I’d have to check” etc.

The South China Morning Post calls them “Urban administrative officers”but I wouldn't be surprised if a few other terms had been used.

In this AP story: link, they use “urban inspection force” and then “urban administration bureau” the next par.

Hope that clears things up.

So their whole purpose is for "keeping order"? Besides that they do nothing else? In that case...

If you're going for sinister, I'd just call them "Agents."

More bureaucratic and no less cynical, the Harmony Police.

Municipal Task Force Agents? MTFA for short. Or Riot Police. Stormtroopers. Shock troops. I'm full of ideas.

the grey blurs?
I'd liken them to the city officials in the uk (ie. gardeners and park keepers) who are now uniformed and perform semi autonomous police work. These guys, in a bright light, could also be Elliot Ness like, cracking down on counterfeiters. But that doesn't happen very often, nor without a warning phone call.
Perhaps just call them grey cops, to distinguish them from blue or green ones?
As for the definition of how cop-like they are, thats for the professionals. Another way to describe them could be 'special municipal law enforcement officers.' SMLEO

"Urban Control" is I think most literal- and serendipidously descriptive.

I'd succeed it with officers, squad, agents, or what have you for clarity.

city managers seems like the most direct translation.

How about "constable," which is defined in Merriam Webster as:

"3. a public officer usually of a town or township responsible for keeping the peace and for minor judicial duties. chiefly British : police officer; especially one ranking below sergeant"

Although in my head, a constable has a sort of jolly, quaint connotation. It doesn't square well with the cheng guan's thuggish image.

Goon Squads

city guard, urban police, city-babysitter, urban management officer/personnel

those r the words i can come up with. hope that helps^^

If we follow Pete Braden above, we can revive the old British joke, "You're the men who put the 'cunt' in 'constable.'"
I have tended to use 'urban management' myself in the past, but am liking the suggestion 'urban control' - has the necessary brutal edge.

Hawker Harassers?

Small Business Patrol?

The thing is, they are not "rent-a-cops" as they are actual government "officials" but their jurisidiction and powers are very limited. They mainly make sure illegal vendors/hawkers aren't creating messes and blocking sidewalks or pedestrian bridges and enforce some unclear rules on legit businesses like small cafes from having outdoor seating (usually by confiscating chairs, tables and umbrellas) if in fact they are not licensed for that al fresco experience.

It's probably one of the crappiest jobs in Chinese officialdom as they get no cooperation from the cops and respect for them is minimal by the general populace. I'm sure their behavior varies from city to city...

Thugs suffice for me.

I actually quite like "parapolice", because though it doesn't have any correlation to the Chinese name, it pretty much describes who they are and what they do. I've seen it pop up in a few periodicals, and I figure it will emerge as the consensus term for just about everybody but Xinhua.

City administrator is a bureaucrat and a city planner is more of an engineer or designer of transit systems, zoning plans and the like.

I believe the best term is "auxiliary police," which in the West is often someone who deals with 'nuisance offenses' such as littering or illegal vendors but is not a full-fledged law enforcement officer. Auxiliary police aren't usually paid in Western countries, but they do occupy this middle ground (not civilians, not law enforcement) similar to the chengguan.

Here's how Hong Kong (which does pay auxiliary police) defines the role: "a trained manpower reserve to support the regular Force in its daily performance of beat patrol duties and in supplementing normal police services during the policing of major events."

link

I've always called them "City Patrol". I know it's not very accurate, but it works in my conversations.

"Urban control" as both noun and verb is most apt by being true to the original in translation and intention. Does any native speaker of English not intuit the perniciousness of "urban control", not sense its implied meaning of sanctioned thuggery?

The response by Liz hits it on the head (Ouch!) and inspires this attempt at an accurate translation which literally defines the 城管's sole duty:
"beat patrol"

urban control officers gets my vote

And "urban control officers" still works with the old British joke ;)

urban management authorities

In the last paragraph, Howard French calls them municipal agents.

link

I'm warming up to "beat patrol", as suggested above.

I once used "city guard" for those bastards,something like Red Guards.