A wireless communications system includes a radio network facilitating wireless communications with a wireless subscriber unit, a dispatch application server providing dispatch communications services to the subscriber unit via the radio network, and an IP Multimedia Subsystem (IMS) infrastructure including a Proxy-Call Session Control Function (P-CSCF) and a Serving-CSCF (S-CSCF). The P-CSCF notifies the dispatch application server of subscriber unit registration events, allowing the dispatch application server to provide dispatch communications services without initiating a separate registration process. Dispatch communications are routed between the wireless subscriber unit and dispatch application server through the P-CSCF, bypassing the S-CSCF of the IMS infrastructure.