Sure as long as you have enough HBAs.
Assume that you have 2 HBAs in the tape unit at the moment and those are connection to SAN fabric 1. You then add two more HBAs and connect them to SAN fabric 2. The SAN fabrics are still seperate, the tape robot is simply a device on each of them.
As long as your backup software has the needed info for each storage array or servers then you should be fine.
Also, with NetBackup, I think you will need an SSO option.