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.
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.