You are right - I cannot seem to find any document that says 'you need the following for Exchange 2007'.
If I combine all available docs and TechNotes:
ftp://exftpp.symantec.com/pub/support/products/NetBackup_Enterprise_Server/292587.pdf
Lists the following:
Exchange 2007 has these predefined groups that manage Exchange configuration data:
■ Exchange Organization Administrators
■ Exchange Recipient Administrators
■ Exchange View-Only Administrators
■ Exchange Server Administrators
I guess it is implied that you need all of them.
The following TechNote lists permissions required for Public Folders, which are normally the same as for mailboxes (except for Public Folder Admin) and seems to confirm my assumption of the above:
http://seer.entsupport.symantec.com/docs/336177.htm
Note: To perform the following Exchange Administrative functions, it may be necessary to logon to the Exchange server with an account that already has FULL Exchange Administrator permissions.
2) Grant the user account "domain\symantec" the Exchange Administrative Roles required to backup Exchange 2007 Public Folders
* Open the Exchange Management Console.
* In the Exchange Management Console, select Organization Configuration.
* Right-click on Organization Configuration and click Add Exchange Administrator.
* On the Add Exchange Administrator page, click Browse and selected the account "domain\symantec"
* Select following Exchange Administrator roles
-- Exchange Organization Administrators
-- Exchange Recipient Administrators
-- Exchange Public Folder Administrators (important role for Public Folder backups)
-- Exchange Servers
-- Exchange View-Only Administrators
* On the Add Exchange Administrator page, Select the server(s) to which this role has access, click Add.
* Select the servers where the public folders are located and click OK.
* Click Add.
* On the Completion page, verify that the delegation was successful and clicked Finish.
I agree it does not really makes sense if you only need to backup your Exchange server. Maybe log a call with Symantec Support for clarity?