that you can import images from older versions of NetBackup (although there are limitations) & also from BackupExec, then you should have no problems at all.
To quote the Admin Guide for 6.5:
"...
NetBackup can import backups that have expired, backups from another NetBackup server, or backups written by Backup Exec for Windows. (Supports Backup Exec versions 7.0 through 9.1.)
..."
Although (not relevant to you but just thought I'd add this!):
"...
NetBackup does not support reading Backup Exec media that written by Backup Exec for NetWare.
..."