I've been following http://seer.support.veritas.com/docs/264815.htm to restore an old database to a RSG, but what worries me, how does Backup Exec and Exchange know that this database I'm restoring will restore into the RSG and not the live Database?
I recently had this concern too but it works.
Look at the properties of the live database in Exchange system manager.
Under <database> there is an option "This database can be overwritten by a restore".
The default is for this not to be selected. If this is the case then you know that you should be okay.
Similarly this option should be selected (and possibly greyed out) in the properties of the equivalent RSG databse that you've created.
If you have problems mounting the databse after restore then this may help:
You could wait until the day after a successful full exchange backup just to be on the safe side!