Hi Steve,
We have many of these type of setups
You'll need to remove the DID from the actual phones and replace it
with a new number on the same phones.
Then create a CTI-RP on CUCM with the DID number, use the Forward-All
to voicemail to get the calls over to Unity/Unity Connection. Have the Call
Handler route the calls back to the newly created "shared" line after the message is played.
So, let's say the DID on all the phones is 5555. Remove 5555 from the phones
and replace with a new number like 2222 (does not need to be DID). Create 5555
as a CTI-RP and route to Unity/Unity Connection, create Call handler as 5555
and route calls to 2222 as required.
Cheers!
Rob
"Celebration it's around us, every nations, all around us.
Singin' forever young, singin' songs underneath that sun" - K'naan