I've seen people mention that on AP1, the rear camera is not even connected to the computer/hardware the processes AP - is the same true for AP2.0 / AP2.5? With V9.0, Tesla talks about that all 8 cameras are now active for 360º "vision", which would include the rear camera, and would imply that the rear camera is part of the camera group used for AutoPilot.
It’s used on AP2 for sure. If a car gets close to you from the rear, the new surround view renders the car behind you!