NetBackup may have Veritas Private Branch Exchange (PBX) shared environment with other Symantec products, as example VCS, OpsCenter.
When NetBackup is installed in VCS server, PBX will be upgraded automatically if NetBackup PBX version is later than VCS.
For example, when attempting to install NetBackup 7.0 in VCS 5.0 cluster, the existing PBX version (1.3) is upgraded automatically to later version (1.4).
In PBX shared environment NetBackup and other Symantec products, Symantec products support PBX upper compatibility. Basically Symantec support such environment.