Deeps is right ....
first let me be very clear on licensing, SSO is based on drive, not on server, single drive you can zone to n number of servers.
so taking into this account, zone you tape libraries so that master server( two nodes), media server 1 and media server 2 see the drives.
now make the master server as robotic control host for both the tape libraries, so that u will have 4 storage units created, 2 for tape libraries one and 2 for tape library two.
now when in normal backup window use local tape libraries connected to each media server, when in case of single media server failover, just chaange the storage unit in the policy or go for storage unit group so that it automatically takes the other tape library for backup.
this was tested and put in place, let me know incase of more doubts.