The Mountie I was talking to did call me back. Was unable to get hold of the senior Traffic guy at the time to get a proper answer. I will try again in the new year. I spent my camera money on a second SiO2 battery so the camera idea is on hold for now.
Good idea to have one set of camera and display with two wiring sets. I did that with my Trimetric battery monitor, where each RV has the shunt and wire and I move the display back and forth. I used four-pin trailer connections on the Trimetric wiring so it is easy to plug in the display in whichever RV I need it. I don't know what sort of wires these cameras use, but some version of that would work. Maybe MC4s or whatever.
Kind of dumb to put the camera in a truck's tailgate. I never used our OEM tailgate when we had the 5er (had a 5er type with the notch), and not with the truck camper either.
There must be a plug-in for the camera when you take off the tailgate, so that would show what kind of plug-in to use.