I passed by this experience when i was setting a new protection group using DPM 2012 for the latest SQL database server 2012. As per Microsoft System Center 2012 – Data Protection Manager Release Notes http://technet.microsoft.com/en-us/library/hh848297.aspx DPM 2012 should backup and recover SQL 2012 Databases except if the AlwaysOn feature is enabled. The AlwaysOn feature is not supported under the current DPM 2012 RTM but expected to be fully supported with the release of the System Center 2012 SP1 (expected in the next few weeks).
Briefly, To backup and recover SQL 2012 workload under DPM 2012 RTM
Make sure the AlwaysOn feature is not enabled (Currently DPM 2012 RTM doesn’t support it)
Grant the SQL NT AUTHORITYSYSTEM account SysAdmin Right.
Remove the Protection group and add it again after applying the above changes.