Edited after I rewatched the video:
1. Tower handed them off to departures.
2. They said bye and stopped listening to tower.
3. ITA veered left.
4. Tower noticed it and warned them, hoping they are still listening.
5. They were evidently not listening to tower anymore, and did not contact departures yet, when they noticed traffic themselves.
6. They greeted departures saying they see traffic, and veered left.
Later at 2:45 American said tower didn’t give them a heads-up. The fact that departures asked them about it could mean that departures thought they were still listening to tower.
Pretty sure the pilots have a second radio and could be listening to both departures and tower during handoff, but it’s unclear whether that’s routine. If they did it, they would have heard tower’s original warning.
> I believe their avoidance maneuver was a climb change.
According to the chart in the video, AA veered to the left. This maneuver started around 1:51 in the video, which is at least 10 seconds after tower warned them of traffic and instructed to stop the climb for the first time around 1:38.
I don’t know if they stopped the climb around 1:38. If we know for sure that they stopped the climb around 1:38 when tower told them so, then there is a good chance they were indeed still listening to tower and heard the traffic warning. If that’s the case, maybe they thought that stopping the climb 10 seconds earlier was insufficient (and tower was wrong about it).
Unless it is out of sync by tens of seconds, however, it is clear that they were handed off to departures and were neither responding nor even listening to tower.
Of course, ITA paid even less attention, considering how they were the original cause of this all and how for 30 seconds they ignored ATC’s request to turn right immediately (issued at about the same time that AA was warned about traffic).
This doesn’t contradict that what AA did was proactive and possibly life-saving, but I have a feeling that the initial deviation by ITA could have been benign if both crews paid their full attention to comms: ITA started to turn 270 immediately as they are told to (while continuing to climb up from 1500), and American stopped their climb at 1500.
(There could be errors in the above in case the chart and different radio communication tracks in the video are out of sync with each other, which is possible.)