We have the following Scenario:
B and C are in a Call Pickup Group.
If someone with an external number calls C the CURRI Response for those calls is always divert to D.
An external phone (A) calls an internal phone (B) -> CURRI Request from CUCM and Response with continue
B is in a call pickup group with C and C tries to Pickup -> CURRI Request from CUCM (Calling Number: A and Called Number: C) and Response with divert (because of the external number)
Why is there a CURRI Request from CUCM during the call pickup?
In the configure external call control guide (CUCM 11) on page nine you can read the following:
When a phone user tries to pick up a call by using the Call Pickup feature, External
Call Control is not invoked; Cisco Unified Communications Manager does not send
a routing query to the adjunct route server for that portion of the call.
I'm thinking you will need to look at the traces to see exactly which leg of the call is diverting the pickup request. There are also multiple types of pickup, so it's possible there is some documentation confusion around this point.
I'm afraid that I haven't experimented with this exact call flow, so these are my speculations...
I think the phone calls the "Call Pickup Group Number" when you press the pickup softkey and if CPG number is on ECCP policy so the call will be inspected by router server.
I'm not sure if it's real true, but is logical.