As a matter of fact, I got part the way through this today. The camera is a numberplate mount version. I ran the camera wire up from the number plate through the right number plate light and into the tailgate area. I did have to pull the tailgate trim off.
I then run the wire inside the tailgate up to the hing points and then through the left flexible rubber connection and into the roof lining area.
I then run the wire to the left between the roof skin and the lining heading down and behind the boot area trim. It then got dark and I couldn't see to well, so I will finish it off tomorrow.
My intent is to run the wire inside the trim all the way to the front where my GPS/DVD/Radio unit is.
The only body work I had to do was take a small nick out of the plastic where the number plate light is actually fitted. The nick is the same size of the wire, and will never be seen. You do see perhaps 2 inches/5cm of wire as it goes from the camers upto the numberplate light. All in all, quite happy so far.