For about two years, RTC and its bus drivers have been fighting over a plan to switch on the audio capability to the cameras already on transit buses. Teamsters drivers say it’s illegal eavesdropping, and neither side seems to think an agreement is possible without involving a federal judge. RTC’s Joe Harrington says the issue for them is safety and security. Drivers cite a law that forbids the recording of conversations unless at least one of the participants grants permission, and they say they don’t.