Sadly, Pickup Notification only works with Primary Lines
For CUCM 7.x (***)
Call Pickup Notification
The Call Pickup Notification feature provides an audio or visual, or both, notification on Cisco Unified IP Phones when other members of a pickup group receive a call. Call Pickup Notification gets configured in three configuration windows for three types of settings: system, call pickup group, DN/phone.
Service Parameters Configuration-The type of audio notification (beep or ring) to be heard when a phone is idle or busy gets set from the Service Parameters Configuration window. This setting becomes the system default.
Call Pickup Group Configuration-The type of notification for each call pickup group gets configured from the Call Pickup Group Configuration window in Cisco Unified Communications Manager Administration. In addition to configuring the type of notification, you can configure the time, in seconds, to delay the audio and visual alerts after the call comes into that group. This allows the original called party a chance to pick up the call prior to the audio and/or visual alert being sent to the pickup group. See the "Call Pickup Group Configuration Settings" section.
-To configure whether the notification will be audio or visual, or both, use the configuration settings in the Call Pickup Group Notification Settings section of the Call Pickup Group Configuration window. ***The notification gets sent only to the primary line of a device.