Hi there,
No you can't. Unfortunately you cannot share a SCSI-attached tape drive so that it can be used as a backup device on another server.
You could share disks, and a tape library if you had a later version of BEWS with a SAN in place (SAN SSO), but there is no work-around for a SCSI tape.
What you could rather do is transfer BEWS 9.1 to the server with the tape drive, and create jobs to backup the other server to the disk array, and then once a week backup to tape.
Your current scenarion doesn't allow it though.
Laters!