My V6 limited came with heated mirrors and according to the Toyota Canada brochure on page 10, all models, even the base 4 cylinder model, has them. They come on when I turn the rear window defrost on. I guess they ran out buttons so they share the same one. I had to look it up in the manual today because I was looking for a separate button.
Yeah some dealers are clueless. When I was shopping for the RAV, the dealer told me that the heated mirror was an option on all models. I had to inform him that it was standard only on the color keyed mirrors of the sport and the limited models.