i just helped a friend install in a 2013 BRZ limited not sure how much the radios have changed from model year to model year, but a couple of time savers.
http://www.beatsonicusa.com/bcus3-536.html
we used this harness it plugs right in to the back of the radio.
**** IMPORTANT NOTE****
The camera must be powered up before the radio powers up otherwise it will not see the camera at all. We took care of this by powering it off of a ACC source on the amp harness in the truck.
All you have to do is run the RCA from the camera to the harness on the radio and you are done. super easy.
This was for a 2013 BRZ Limited so take it for what it is worth.
I figured i would try and help save some time and headaches.