I don't know how long that frequency stays open but one day someone in the KSTP News Room left the transmitter, for the Live Shots Setup (450.5500), wide open for about 30 minutes and I was able to overhear what they do to get things ready for the Twin Cities Live show.
Also a few times a day the IFB bands for the news stations re-transmit the audio for the TV show on currently. I have to temporary lock them out all the time.