Yes, but the backup will have to be carried out on the AIX box in order for it to have access to the tape drive.
Check out
Mondo, which can backup to CD, DVD, and tape.
The sort of process you would need to do would be:
Mount the directory from your HPUX box (via NFS or equivalent) on your AIX box
Use Mondo to back that directory up to tape
Unmount it again