You only have to open your Uber Rider app to see that all fares are significantly subsidised. That has to be a threat to his core limousine business which can't be easy if you've spent years building it up.
However, I don't see how he or any of the other union officials (assuming there are others) can expect Uber to negotiate with a competitor. He, himself, offers fixed price taxis yet he doesn't (to my knowledge*) drive a taxi. It'd be like Free Now telling Uber it represents the 15,000 drivers it employs and expecting Uber to negotiate driver remuneration with them.
*Badge M0259 associated with Limo plate 56667 according to TfIs Driver Check app.