I haven't much explored in this area but went through the some concepts related to eMBMS.
MBMS Service Area's are configured statically (ranges 1 to 256). Each cell which can serve for mutlicast services, has at least one MBMS Area Id (1 - 256). An MBMS Cell can be part of up to 256 MBMS service area's. Please check "M2 SETUP REQUEST" message for the reference.
MBMS Synchronization Area is associated by MBMS service. All cells belong to MBMS synchronization Area are tightly time synchronized then all of them transmit same content over the same radio resource i.e. time and frequency both by using same MCS.
As I mentioned above, I am new for eMBMS. So please correct me if required.
