A system provides push-to-talk (PTT) or similar communication service via a radio access network providing wireless mobile packet data communications for mobile stations. A server distributes packets of digitized audio received from a broadcasting mobile station to one or more client devices of other parties. The called client device(s), however, may not all have the same communications capabilities as the broadcasting mobile station. Signaling procedures are adapted to inform the broadcasting station of the capabilities of the other client device(s). This enables the broadcasting mobile station to configure its transmissions of digitized audio through the network for compatibility with the capabilities of the other client device(s). Proper configuration avoids loss of data at the destination, particularly at the start of a PTT transmission, due to transmission in a form or configuration that may be incompatible with one or more of the receiving stations.