Would it not be easy for all drivers who receive a ticket to look at the history of passengers they've picked up, and look for commonality to determine who the "undercover op" was? Then blacklist them, and problem solved.
Seriously though, what blows me away is that the mayor and everyone keep citing these "insurance reasons" etc for why it's illegal instead of fixing the root of the problem which is the crooked taxi mafia and lack of decent public transportation.
Soon enough however, people will vote with their wallets and they will have no choice.