1) Do you mean for the NY 'tower' feed? If this is what you mean, the tower scanenr monitor the tower frequency, in which the tower itself controls around 5 to 7 miles from the airport and the runway itself. Further away from the airport, the planes are handed off/from to either departure frequency, arrival frequency and or ground frequencies. Those are monitored on other feeds.
2) Yes, they do shut down the engine while waiting in line, most of them are advised by the tower though, if the tower think the wait time will be long. They are advised in advance on when to start up the engine again once the line are beginning to move. Main purpose is to save gas = $$ and the environment.