Since it doesn't use the interior camera for actual driving perception it doesn't seem like it'd be an obstacle to send an additional signal over the existing wires and let the computer filter the data.
I could be way off, but I'm thinking in terms of how trivially 2 devices can transmit over the same an ethernet cable from a hub to a switch even if the other end goes into a single port on a switch then the switch handles getting each signal to the right place.
tagging
@verygreen as he'd likely have far more insight on this.
It's likely US regs will be coming too (esp with recent NHTSA announcements)- but this same AP camera swap will be need on EU S/X as well won't it- they did sell em there in 2016/2017 AFAIK.