When i ordered you had to get the "siktpaket" (which included fog-lights, autodimmed rearview mirror and something else i dont remember) with this package you got heated mirrors and washerfluid-nozzles.
In fact i think it was enough to choose the foglights alone to get the heated mirrors, a bit weird
as far as i know it was not possible to get heated mirrors as a standalone extra.
But they seem to be a bit weak, takes too long to get rid of snow/ice fog/rain i think. And in the case of just rain it never dries up. On other cars i've driven the mirrors remain clear and dry with perfect visibility in rain, but that's probably too much to expect from a "premium" bmw