Mapped drives are specific to a logged in user, so that's not going to work, as impersonation doesn't log in a user in such a way that drives map.

Also impersonation doesn't "hop" over a process boundary, so when you try to access a remote resource impersonation will not escape to that connection.

So, rather than trying to run the PVCS command line (I am seriously shocked people still use PVCS!) you could try an SDK if they offer one?