Assuming your VPN is over the Internet, and encrypted , all LAN to LAN traffic would typically be allowed to pass, unless your mapped an ACL.I set up PC anywhere to work on a router, using an extended access-list on the serial interface (inbound). I ...
If you need to make this simpler for the users,I recommend a batch file that will ftp in, passing username/password, then quit out. The next step in the batch file would be a net use statement.