If the cabbies complain loud enough I'm sure they can set up a sting. Nothing stopping them from downloading the same app and hailing a ubercab. When you can't present a medallion or commercial drivers license you're busted.
And there is nothing stopping them from going into court and throwing water on the whole thing with an injunction.
And there is nothing stopping them from going into court and throwing water on the whole thing with an injunction.