Apparatus for an echo canceller, and an accompanying method for use therein, for improving voice performance in handling mobile-to-mobile calls in a GSM environment, specifically with a base station controller (BSC) at each end of a call path where one BSC supports tandem free operation (TFO) and the other does not. Here, each canceller has a capability, through unique in-band messaging carried by robbed-bit signaling, to communicate information with its peer (distant) echo canceller across the call path so as to permit each canceller to coordinate its operation with the other, and particularly to enable a specific voice enhancement feature set optimal to a particular type of call, e.g., mobile-to-mobile, and without adversely affecting the TFO protocol.