[scottmcphee]

Anyway, no point in doing more tests at this time. The only way this could happen is if I get my mitts on a car and scope it out closely.

If anyone else wants to take this on, I bet there's a way to generate a CAN message or streaming messages that cause windows to up/down.

Or maybe start by finding the LIN message that sends ACC ON command to drivers door. This cmd would flow through to the passenger door on UART as an ACC ON command to passenger door. Then sniff the UART while doing passenger up/down using the drivers master switch for that window, it will be a stream of repeated commands while holding the switch that stops streaming when let go.
Then see if the passenger side switch does any kind of communication over UART to the driver's door while the passenger works his window.