Here's the verdict. I was able to get myself out of bed to test for voltage at the two leads on the back of the mirror glass. There is NO VOLTAGE present with either rear defrost or the MAX defrost enabled. We do have the necessary wiring to the plug in the door up to the mirror housing and also the fuse is installed in the under hood fuse panel. It either has to be enabled by your Ford dealer,(like Bigbot45 suggested) or I'm missing something entirely by not having a wiring schematic in front of me.
13 Triumph Tiger Explorer