& indeed that's how we've still got ours set up.
However, if you look in the
NDMP Admin Guide it confirms that you can configure Netbackup to make backups to Media Manager storage units.
"...
Using remote NDMP, you can back up NDMP data to a configured drive in a Media Manager storage unit on a NetBackup media server. The drive can be used for both NDMP backups and for non-NDMP backups.
..."
Basically point the NDMP policy to a Media Manager configured storage unit. Not sure how much of a performance hit you're likely to get tho'.