Correction - it appears that when in game integrated radios operate as intended. I am unsure why they do not show up in the DCS dynamic radio options menu in game options. @BIGNEWY not sure if this is due to a bug in core DCS or of the Mirage module?
I can confirm the TRAP-136 + TRAP-137B operate as intended with Radio one PTT operating either radio depending whether green or red radio is selected on the left console.
Aarnoman's post in Mirage F1 (all variants) currently do not have native integration of DCS voice chat radios. was marked as the answer