In the case of the Celerra you can set the format to tar, by setting the 
appropriate directive, through the files tab of the policy.  This is the 
bit:

<<
To enable path-based history, enter the following at the top of the list 
on the NetBackup policyâ??s Backup Selections tab (file list):

set type = tar
>>

Although this talks of path-based history, it does in fact tell the 
Celerra to use tar format, as per the NDMP specification.

The "VERITAS NetBackup for NDMP: Supported OS and NAS Appliance 
Information" document defines the settings available for each NDMP 
appliance type.

But....try before committing to delivering a service on this...

If you really need to save money you can use the local server_archive 
command to write tapes, and can schedule running that by using cron jobs 
on the Celerra...but that would not help with plain old file restores, so 
I can't see that being useful.   The idea of paying for a Celerra and then 
saving money is odd!

William D L Brown