I think i can say yes to that one on behalf of the official SG guys, the camera housing are just waterproof thats the only thing that set it apart from the regular cameras.
And the parking guard routine are handled in the main unit so as long as it can get footage from a camera it will also be able to do parking guard with that cameras feed.
Feeding the wire i would be careful, while not cheap garbage SG use, it do seem like you can be too rough with the wires, i would think not least where the wire are bend sharply.
Other people have managed with the regular cameras on SUV hatches ASO to feed the cable thru the rubber grommet that have the cars original wires too, without any problems.
I have also done this myself with the wires to my 2 side cameras that are on a fixed piece of glass on my rear doors, so i have fed them down thru the door and on via the rubber grommet to the B pillar.
And so far that have been working fine for a year now, though again my car dont see much action on the rear seat so the doors are not used much.