thanks fabian, i can admit i sometimes need to backup directly to a remote that has been synced, so i bulk edit switch between the sync user and backupuser. Perhaps it helps somebody to know until pbs has a clean way.
ie:
cd pbs/vm
sed -i 's/backup@pam/backupuser@pbs/g' */owner
or
sed -i 's/backupuser@pbs/backup@pam/g' */owner