In an embodiment, a multicast communication session is setup at an access network within a wireless communications system, whereby the access network transmits an announce message announcing a current multicast communication session to a given group of access terminals within an initial cluster of sectors. The access network receives a registration request for the current multicast communication session from an access terminal, and selectively loads a stored cluster of sectors that supported a previous multicast communication session to the given group. The access network then turns on a multicast flow for the current multicast communication session within each sector of the stored cluster. In another embodiment, a multicast communication session is terminated whereby the access network stories a formation of the engaged cluster at or near the termination of the current multicast communication session, which can then be used during setup of a subsequent multicast communication session.