How is bluetooth phone mute implemented?

I use the bluetooth handsfree phone feature alot. I tend to use it to call in to meetings while I am commuting, and most of the time is spent listening to the meeting, i.e. not talking. I hit the 'mute' on the MFD to make sure that my road/background noise does not bother others who are called into the phone conference/meeting.

When I do need to talk, I take it off mute, say my stuff, and put it back on mute. That seems to help the phone conference system so that I don't accidentally squelch someone else out with my background noise.

The problem I have, though, is I'd like to have something closer than the MFD to control the mute. The steering wheel would be a great place, I wish the 'talk' icon button on the steering wheel acted like a mute toggle. Since that's not the case, I'm wondering how to implement something myself.

I am not sure how the mute is implemented, however, and looking for some input and advice.

Looking at the wiring diagrams from the service manual, it looks like the headliner mics are connected to the MFD. Is that correct?

I remember seeing a thread about someone adding a second mic to their headliner, and I think I remember there being a small mic amplifier up in the plastic area. I'm assuming that the mute function is NOT implemented at that amplifier, but can anyone verify that?

Finally, does anyone know if the MFD is essentially disconnecting the mic, i.e. internal to the MFD, or is something being done at the amplifier under the passenger seat?

Thanks,
Mike