The master server will need a Netbackup Enterprise Tier 1 server license.
Assuming that the media server at "Y" is also going to backup other servers (not just itself),
the media server at Y will need a NetBackup Enterprise Tier license.
The tier level depends on the server model.
Each tape drive within the tape library at "Y" will need a NetBackup Library Based Tape Drive license.
If the vault feature will be used at "Y", vault licenses need to be included for those tape drives.