I've no idea, I also saw some mention of it on the Csound list, but have no idea where it is at.
Can Csound/Cabbage be used to create a vocoder? Certainly. Check out the vocoder example that comes with Cabbage.
I don't see why not. Sure. Anything is possible with OSC.
Yup. You can convert any a-rate signal to k-rate and ten send it where you would like using OSC.
Are you familiar with Csound? If not I'd suggest checking out this online resource. There is also a section on OSC there that might be useful. If you need help with any code let us know.