In Houston each driver/tow company has a coin and a cop at the scene puts all the coins in a hat and draws how ever many are needed. So for a two car wreck you get 15 tow trucks and they pay no attention to normal traffic laws.
WITH THE exception of the coin thing, it's the same in philly.
in nj, the state police take bids from companies. the company i used to work for had an area that covered about a 12 mile radius from the shop. we were in a "rotation", meaning that they'd call us for the accident on rt. 42, but if another happened a mile up the road, the next company in the rotation got that call, and so on.
most townships and boroughs do the same thing. the company i worked for lost their towing privledges in gloucester twp., because he had a very arrogant/violent black lady, who started throwing racial slurs at him, while her son went outside and called the police.
the hispanic cop walked in the front door, just as he lost control, and returned the racial slurs to the lady.
thing was her car had been impounded because the son was caught driving drunk........