I take it that a signal-event post-upgrade ; signal-event reboot didn't work either?
I have done this in a test environment only. If you have re-created all of your users, ibays and previous environment, and if all you want to do is then move/copy their data:
User data is stored in /home/e-smith/files/users - make sure you adjust the permissions correctly. If you have issues with mail, you may need to delete the users /Maildir/dovecot* files, they will be recreated on the next login
Ibay information is stored in /home/e-smith/files/ibays - again adjust permissions.
John