I have seen it both ways with my experience in other cars and adding optional accessories after the fact. Meaning, I have seen it where the wiring harness is there and after buying the accessory, just plug it in. I have also seen it where the wiring is NOT there and I had to add the wiring hardness myself.
My suggestion is to pull the rear hatch trim (from behind) and see just what's in there. From memory, there were a few clips to pop out and then typically just pressure clips that hold the trim in place. With the trim removed, you will most likely see what wiring is there. There definitely will be wiring for both the wiper and the trunk release button. So look around from a component that looks like its not plugged into anything - that is typically the tell-tail sign that something can plug in there.
If you can find a schematic of the car, that will also tell you. Perhaps someone with a service manual can chime in.
With that being said, I would place my bet on when you get the camera plugged into the wiring harness, it will begin working right away. I find it highly unlikely that there's anything software related in the nav unit. In fact, if you go into the secret settings menu (turn off radio, press Map three times, Radio Power two times, Map once - quickly) you can go to the camera settings (select Confirmation/Adjustment --> select Camera) and see if they are there.
Color: Cayenne Red
Plate: I PLGIN