The PBX service is a required service for netbackup 6.5 to run. Since the move from a file based information system to a sybase service, and also for consolidating the number of processes running on a specific "port" of communication, the PBX service was registered on the public port registration for what it does. Whatever you do, do not uninstall this as EMM and other services will not work properly or at all.
More documentation can be found if you google "The difference between Netbackup 5.1 and Netbackup 6.5"
