You should be able to restore a single mailbox using the standard Recovery Storage Group procedure. This involves creating a Recovery Storage Group and using the FLR appliance to restore the backup copy of the message store that contains the mailbox you want to restore. Here's a pretty good article that describes the process:http://www.msexchange.org/tutorials/Wor ... -2007.html
We use a third party tool that allows for direct extraction of mailboxes from the message store database. We "short circuit" the requirement to restore the message store by starting the FLR from within Veeam and then minimizing the Veeam restore browser and running the tool directly on the mounted volume. You might be able to do the same thing for a Recovery Storage Group but I've never tried it.