Sorry for your problem, I maybe able to assist you. I am not familar with the cooper BCC, but almost all the time on all cars the tail lights are feed by a single wire from the front of the vehicle. left,right tail light and license light are all on the same circuit. Your car is 10 years old I would think corroded connector or broken or rotted wire. If all of this fails you can run a new wire from the left to the right tail light, this will work and cause you no problems and save you many $. Hope this helps you. Jim. Don't be afraid to questin me more.
I wish you were familiar with this particular car and the BC1 body control unit.
I have never had a seperate wire on anyting from the source of power in the front to the tail lights. If you still think it's the BCC check allo fuses I have found there are fuse that are not labled for specific pourposes ie bc1 lablel. Im sure if 1 tail light lights and the license plate light work also you have a wiring problem. If you wish i'll opt out so another expert may address your problem. Thanks For using just answers. Jim