BE2012, CASO and DataDomains

I was wondering if anyone had experience configuring the following

Site 1: (Primary Site)

1 x BE2012 Server with CASO

1 x DD

All licenses for DDBoost replication etc

Site2: (DR Site)

1 x BE2012 server and media agent

1 x DD

All licenses etc...

What im looking to find is the best soltuon to have the secondary site available in the event the primary site goes down. 

Also if the primary server fails i want to be able to have the secondary server kick in and start backups.

Do i need to re-register all BE agents with the secondary server to enable them to backup.

Does DD replication or BE2012 CASO handle replication between the two DD's?

Any help/advice would be greatly appreciated.