A method and system for providing supplementary services for a wireless access network includes downloading supplementary service triggers from a call agent to a mobility control function (MCF) for a wireless access network. Wireless-specific signaling of the wireless access network is communicated to the MCF. The MCF detects events associated with a trigger based on the wireless-specific signaling. The call agent is informed of the events by the MCF through session initiating protocol (SIP) extensions.