Well, after talking with the lead installer at the wireless shop (Verizon) it looks like this hands-free install has no stereo mute line at all. The unidentified wire is a horn remote to make the horn blow when the phone rings (for contractors/surveyors and the like). Looks like I'm on my own on this one, I'll probably try and tap into the little speaker's wire to see what sort of voltage it's got, maybe I can rig a relay setup somehow...we will see. I'll post what I find.

-Zeke

just say you weren't paying much attention...