Since COMO don’t support "voip" and relay on the pstn network you will have to configure dual forking or something so that the call gets transferred to the user’s cell when someone calls or simultaneous ringing, this is basically the same as what you ask for but one less step since the user gets a call, and accept or reject (call details can be posted by MOC into Outlook for info about the calls). So I don’t really see why you want the extra step of information being sent over the data channel to the phone just to see that a call is coming for you. Other than it’s just a cool feature so I hope it will come together with ip calls over 3g
Regards