From what I can tell, CPS requires periodic full backups of the entire Exchange store, which in this case is 40 to 60 GB. I'm not sure I want to be pushing that much data across a VPN link on a regular basis. Am I wrong? I also don't want to have to do a restore from a backup-to-disk folder when I need that data; I want it sitting on the backup Exchange server in an EDB and STM set (possibly with the current Exchange log files) ready to be mounted or even already mounted (if possible). I don't need instant automatic failover, but I do want no-hassle manual failover that can be accomplished in a few hours at most.
If you have the exchange configured in a Cluster then Backup Exec will/can not see the exchange database as the local resource of one of the cluster nodes and hence not allowing the backup.
However a workaround as I see it would be to stop Exchange services on the server from where you want to backup yoiur Exchange and then backup the .edb, .stm and log files using BE, however this will be just like a flat file backup and will not flush the logs and also at the time of restore it will let you restore .edb, .stm and log files after which you/MS will be resposible for playing out those log files and bringing the database in clean shut down state and mount it.
However, As a Symantec Tech as well as from an Administrator's point of view, I will strongly recommend you NOT to use the above mentioned method.