As far as money is concerned, I can't see a union being able to raise rates at all, to any kind of significant degree.
I guess Uber could be pressured, theoretically, and raise uber x rates to $2 a mile, or more.
But you have to have passengers to actually pay the rates, and passengers are used to paying lower rates. Sure they can be used to paying more over time, but you're talking about a considerable length of time where the supply of drivers will far exceed the demand for rides. People will take the bus, get rides from their friends, walk, contract with lower priced ride sharing outfits that will look to join the market, get rides from taxis both licensed and unlicensed.
The old school idea of government regulating boards running a tight ship on transportation rates was killed dead by Uber.