The following Exchange Powershell comand Get-MailboxDatabase | fl name, *backup* returns empty LastFullBackup, LastIncrementalBackup, and LastDifferentialBackup fields. This is despite successful Exchange full and differential backups.
Additional switch is required to show the backup time.
The correct command to view the backup time is:
Get-MailboxDatabase -status | fl name, *backup*
Notice the additional switch "-status".
NetBackup 7.x.x, Microsoft Exchange 2010.