The described behavior is expected and is documented Cisco bug ID CSCsb12946.
This Cisco bug ID is a Product Enhancement Request (PER). It is possible to request the Pickup feature be enabled, which would provide the ability to use Call Pickup or Group Pickup for calls from members of a Line Group associated with a Hunt Pilot. In order to make this request, talk to a Cisco representative and open a PER.
Based on the Pickup logic, the behavior described in this document is correct and expected. Ideally, the members of the Pickup Group in a Hunt List are not answered. There is a defect in version 4.0(2a)SR1 of Cisco CallManager that enables Hunt List Pickup. But, this defect actually caused a memory leak and left some dead entries in the forwarding manager. Also, Cisco CallManager failed some other Pickup scenarios.
From the code in 4.0(2a)SR1, as long as this is configured, any alerting party is added to the Call Pickup table. The alerting party does not need to have Pickup configured. This behavior is not correct. There is a fix for these incorrect behaviors in these versions:
Refer to Cisco bug ID CSCsa66224 for more information.
With the fix applied, which is the case in versions 4.0(2a)SR2 and 4.1(3)ES, the problematic behaviors disappear. This is why it looks as if the Pickup no longer works on Line Group members.
The Pilot Point or Hunt Group feature can be used as a workaround. There are fewer options than in the newer Hunt Pilot and Line Groups feature, but the Pickup option is available with these.
Cisco bug ID CSCsb42763 tracks the same issue in these Cisco CallManager versions:
One possible workaround for this issue is to assign the Hunt Pilot itself, instead of the Line Group members, to a Pickup Group. All of the Line Group members which are a part of this Hunt Pilot can be picked up with the Pickup Group that is assigned to the Hunt Pilot.
In order to enable this functionality in these versions of Cisco CallManager:
Enter CSCsb42763, in mixed case, into the Cisco Support Use 1 Enterprise Parameter under the new Cisco Support use Only group, and click update. Only the CSCsb42763 value in this parameter enables the configuration in step two. Change the value to anything else in order to disable this functionality.
Go to the Hunt Pilot Configuration page, choose a Call Pickup Group from the dropdown list and click update.
For Cisco CallManager 4.2, the same bug is applicable. The only change is that in the enterprise parameter it is called Unsupported Pickup in the CCMAdmin Parameters group.