I know this would probably depend on the state and city, but do cities have any recourse for monopolistic behavior? For example, say a parking provider buys up all of the parking in the city and begins to charge monopolistic prices for parking. Does the city have any recourse to break up the parking provider, or force them to sell off some amount of parking?
States can, and some states do, have "mini-Sherman" anti-trust laws of their own. Whether a city could have such a law would depend on whether the state had delegated that power to cities. I haven't heard of a city that has such a law, but I haven't really looked.
Or if a state has a "mini-Sherman" law, a city could perhaps bring action under such a law, depending on its exact terms.
Or a city could impose a licensing scheme on a specific industry that also prevented a monopoly, similar to the requirements that many cities and towns place on taxicabs, or on bars. Both of those typically limit the number of units that a single entity may own. So perhaps it could be done for parking.