Market Urbanism breaks down the economics at play.
"Now that's not to say that private operators haven't tried to compete – the outer boroughs' immigrant communities have had robust networks of informal private vans (known in NYC as "dollar vans"), which operate illegally but have been hard to prosecute, likely due to the fact that they are used mostly by linguistically-distinct immigrant communities. The recent cuts even propelled the bootleg bus phenomenon out of its immigrant ghetto, when a brave bus operator named Joel Azumah made headlines by operating a bootleg bus route along routes cut in Manhattan, Queens, and Brooklyn. This experiment was quickly quashed by an unrelenting bureaucracy, but at least it demonstrated the mutual desire on the part of riders and entrepreneurs for private service.
The city's Taxi and Limousine Commission appears to have headed that call, and under the direction of chairman David Yassky is trying to replace at least some of the old bus routes with private buses. Unlike the city's much-abused private van service, where operators are technically not allowed to pick up riders off the street who haven't called ahead of time, the buses would operate with many of the privileges of regular city buses, with the added flexibility of being able to alter their routes to fit customers' needs. Cap'n Transit has speculated that this discretion could be used as a back-door way to expand the private buses' reach to areas not officially sanctioned by the program.
Thanks to Stephen Smith