I had this thought for a while and finally had a need to prove if it worked or not - and it did. It's not a world changing event but proves useful if you don't want to or can't convert extensions to operators to provide zone parking.
- Create DGC Group with analog extension, physical T/R port, as sole member, Auto-LogIN as group type - important.
- Put busy-indicator of DGC on "operator" extension
- Transfer caller to DGC via busy-indicator
- Instruct to Pickup #9 and member extension ( not DGC ) number
- Caller hears ringing, not MOH
- Busy-indicator does not light to show call on "park". But if you set que length to 0 and dial DGC extension, you will get busy if call still "parked" in que, ringing if call picked up.
Like I said, not the greatest trick but it does work. Today it saved me some grief. Maybe someday it will for you. You can have multiple "zones" by using available DGC groups too.