Call Pickup or Shared Appearances

I've setup trixbox 2.6.1 with Polycom IP501 endpoints in a small church. I've got 2 ring groups setup, 600 and 601. 600 will ring 2 phones for 10 seconds then the calls go to 601 for all phones for another 20 seconds before it hits the IVR.

I'm asked if I can setup so that if one of the secretarial phones are ringing, it can be picked up on one of the other phones that aren't in the first ring group.

Can I setup an appearance on the phones that doesn't ring or setup Call Pickup? Documentation is extremely sparse.

I know the endpoints can handle it, but I don't know what will happen if I try to modify the config files so it'll work. Can I do multiple registrations, so 2 line buttons are the extension number (I have all three right now) and register the last so it's a different (virtual?) extension? Thinking reg.1.linekeys="2" and reg.2.address="nnn" where nnn is extension number? I might also be able to change it so it doesn't ring with reg.2.ringType="nn" if I can find a ringType that is silent.

Thanks all,
David