A communication system utilizes an interface terminating at a base station (BS) of a circuit services network and a wireless packet data node in a packet data network and DOS over DBM signaling between the BS and an access terminal (AT), thereby permitting the communication system to tunnel SIP messaging between the AT and an IMS network via the BS and a packet data node and to tunnel HRPD traffic channel information and an HRPD identifier from the packet data network to the AT via the BS. Thus, a handoff of a voice call involving the AT may be initiated from the circuit services network to the paket data networking prior to the AT etablishing a call dialogue with the packet data network.