Are car stereo head unit faceplates interchangeable within brands?

I would never suggest switching face plates from different models of a given brand even if they so happened to snap in and seemingly fit... This part may be a good enough coincidence to convince yourself its gonna be OK however its the part of actually powering the head unit on that can be very iffy at best. The face plate has a preset ui that matches the capabable functions of the deck it snaps onto, if you have a ui on the face plate that allows for adjustments that the deck can't perform (let alone understand) you will have issues most certainly if not physical damage. If you really want to know your best bet is to try and ask the manufacturer who built it;-)