It's an open question and an often-debated one: whether or not Roger Korby, in "What Are Little Girls Made Of?,",was Roger Korby or not--that is, whether or not the android-making process on Exo III can, in some instances (because some are clearly not such, like the false Kirk)transfer the soul + mind. But the crew in TNG just blithely accept in "The Schizoid Man" that the being that is using Data to talk is Ira Graves and not Data. As far as I can recall, there is no suggestion that Data just thinks he's Ira Graves; it's fully accepted that this is Ira Graves. Also--On Camus II, in "Turnabout Intruder," we have a device that can, apparently, transfer souls. We have no way of knowing if that would work for an android body, that is, if the device requires a biological matrix or not, but we do know that the device will transfer souls. So the principle of soul transference, at least, is canon in Trek.