Its not true that all eNBs in single MBSFN area should have same BW.
MCE is responsible to schedule at Cell level, and providing MCH scheduling periods to all the eNBS in that area. Availablity of resources to the commited services should be take care by eNB while admitting the UE for that service. As per specifications 1,2,3,6,7,8 subframes are reserved for MBMS , when MBMS data not present it can be used for normal usage. Hence eNB can know it can serve or not based upon its BW.