It may only be possible if the following is available;
1. That your GSM is doing reverse battery/polarity to the Quintum for answer supervision.
2. Your GSM does not signal the call is connected during that message.
3. Your VoIP provider does not allow media to flow through until a connect is received.
It should be noted that if all above is met, then the caller will not hear anything till the call is actually connected. This may cause other undesirable results.