In the NYC area they are two: BMW Of Manhattan and Life Quality BMW in Brooklyn.
There are about 2 or 3 more in New Jersey and 2 more out in Long Island, NY and 1 Upstate NY in Mt. Kisco!
When I say work in the streets...I mean most Automechanic shops in NYC are usually found in old Manufacturing/Industrial neighborhoods that are now not really good neighborhoods. So there is no law against this. Usually they do it because of lack of space inside trhe garage. I don't mind a guy working on my car in the middle of the day...but at night the usually store your car on the sidewalk in such a neighborhood. That doesn't fly with me.