Well if I understand your question correctly, the bypass is easy. Just ground the parking brake wire out of the HU and you are GTG. Another trick is to override via the HU functions, see :
YouTube
I did both just to be sure all functions are unlocked. Also, screen mirroring while driving works like a champ on the 8500.
Wow, that's a pretty sweet trick! Will have to try it on my 6500...
ETA: It works! I did have to press all the way in the lower-left corner vs 1/2" up and 1/2" over. I was disappointed at first until I moved my press all the way into the corner.
Great info in this thread. Getting ready to install the 8500nex myself with the help of the info here. To confirm/clarify the brake bypass - will the override trick via the HU functions reference above still work if you still had the green parking brake wire from the t02 harness connected to the HU harness from above wiring diagram (green to green), OR do you still need to ground the green wire from the HU and not connect the green wire from the t02 harness? If you still need to ground the green from the HU, can ground it by attaching that to the black ground lead from the HU, and then to the to2 black ground or do you need to physically ground it to some metal? thanks in advance.