what evidence do you have that the politicians have been bought off?
I'm glad you asked, as that gives me a great reason to post a link to Simon Garber. As Wikipedia says, "While in Russia in 2001, Garber became friends with Patrick Daley, the son of long-time Chicago mayor Richard M. Daley. City officials tightly regulate all aspects of medallions ownership, granting permission to purchase medallions on an individual basis. Within a year of meeting Patrick, Garber quickly acquired over 300 Chicago taxi medallions. Garber also hired Mayor Daley's former chief of staff Gery Chico as a City Hall lobbyist. In 2003, Garber used this political capital to start the Chicago Carriage Cab Company and was granted permission to operate the taxi business in Chicago. Within six years, the Chicago Carriage Cab Company had amassed over 800 medallions, making it the largest taxi company in the city."
This is but one example, from one city. A little Googling will easily reveal many more examples.