I dunno...I looked again, but I don't feel like pulling all the trunk/interior liners tracing cables. There's nothing mounted at the front of the car (no rear view mirror wires, nothing on the firewall, nothing on the steering column, nothing on the dash).
I'd just mount it somewhere close to the base unit and make sure it has line-of-sight to the sky. GPS signal doesn't play nice with obstacles.
FWIW, it might be mounted behind the screen in the NAV pop-up for all I know. Seems like a logical place to put it.