I don't think so only one subframe is dedicated/allocated to one particular MBSFN Area. Per TTI one transport block would be send and one transport block corresponds to one MAC PDU. If you look MAC PDU structure carefully then you can realize more than one MAC control element can be included into one MAC PDU.
Each MAC control element corresponds to one MCH scheduling information (MSI). And in turn, one MCH is multiplex of one MCCH and multiple MTCH.
Please correct me if my understanding is wrong.