Avaya has a feature that allows "busy monitor" where someone would have an expansion module on their phone and would have many lines showing up there. They would then be able to monitor busy status on those lines. It is not just a shared line though. If one of the lines is pressed, it Speed Dials to that person.
How is the equivalent achieved with a 7960 + 7914?
The feature you need DSS/BLF is available in CCM 5.x (and later) as well as CME.
Unfortunately, not in any earlier versions of CCM. So you have the either/or choice that you have seen. Eitherconfigure the Button as a Shared Line (to see the status) or as a Speeddial for quick Transfers :(
In CCM 5.x this is a traditional BLF (Busy Lamp Field) which is used to monitor On/Off Hook, Busy/Idle conditions on users phones, as well as having a Speeddial functionality for fast dialing and Transfers.These keys can't be used to answer actual calls.
Cisco Unified CallManager Speed Dial Presence
Cisco Unified CallManager supports the ability for a speed dial to have presence capabilities via a busy lamp field (BLF) speed dial. BLF speed dials work as both a speed dial and a presence indicator.Only the system administrator can configure a BLF speed dial; a system user is not allowed to configure a BLF speed dial.
This differs from the "Old" Shared line appearance setups in the CCM 3.X and 4.X trains that you are running into.
For CME the feature is called DSS/BLF (direct station select/busy lamp field) where you have basically a speed-dial button that also lights up when the person is on the phone.
Hope this helps!