I thought about this once. I believe the wiring in the connectors is different, but if you wanted to dig up all the stuff for them off a junked Limited or something (mirrors, wiring, connectors, and all), you could probably get it done. It would probably be tedious, but nonetheless rewarding.
I think JP has a link to a place on here where he talks about how he installed non-OEM mirrors that were heated, as well as having the < or > turn signal indicators on them. I've been wanting to do this to mine, and he had thought that the wiring harness might very well be in the door panel or under the floor plastic guard by the door (if I recall correctly) - but I haven't taken the time to look for it as of yet. I have an '09.