I used to fly United a lot and several times they kept the ATC feed going on the in-flight entertainment system right through the landing and even afterwards. Several times I listened to ground control on the run up to the gate.
I have heard the same thing, right up to the gate, although at times shut down about the time the wheels come down. I have only heard it on push-back a few times, quite often they do not get the entertainment system all the way on and straightened out until just before takeoff roll.
And naturally, any time there is an announcement it cuts off the audio.
I have also heard them shut down the feed if there is an emergency or incident mentioned on the air, even if it is another aircrafts problem. Example another aircraft on freq had a pax medical emergency, so the feed got shut off, and then they did not remember to turn it back on...DOH! I kind of get the impression that the turn on or off of the audio is part of a secondary checklist, and if they jump the list it gets forgotten.
T!