When using a native move job to migrate to an Exchange 2010 or 2013 target is a 2010/2013 CAS required in the source organisation? (4338302)

The following is mentioned in the Migration Manager for Exchange 8.11 User Guide: "Exchange 2010 Client Access server or Exchange 2013 Client Access server (if applicable) must be deployed in source or target Exchange organization".  Does this mean a 2010 or 2013 CAS must exist in the source if one is already present in target.

No.  The documentation states that a 2010/2013 CAS is required in either the source "OR" the target.  If the target already has such a CAS (as would be expected for any 2010/2013 Exchange Org target) then that is sufficient and there is no requirement for an additional CAS in source.