Everything's possible -- if you wire it up yourself. I don't have heated mirrors in my how-to's on my cardomain but several of the mods there are examples of fitting my truck with things it's wiring wasn't designed for like the Explorer Automatic Temperature Control (EATC) and overhead console.
Why don't you work through it and then share it with everyone else? That would be a nice how-to for the site.
I find it amazing that in Canada they can sell a vehicle without heated mirrors. My 91 BMW 318is had them as stock equipment.
Well I will see what I can do about rectifying this shortfall for our trucks.