Hi Rita,
We have some similar setups where we add a second DN/line for the Managers phone (non- DID) and then configure this new line to Auto-Answer on Speakerphone.This is configured under the Directory Number Settings for the new DN/line. So when a call comes in on their Prime line ext AAAA you can answer the call, put the call on Hold and dial the secondary line ext BBBB, it Auto Answers on Speakerphone and you can let the Manager know they have an important call on AAAA.
Setup one of the Auto Answer DN's on each of the Manager 7960's and you should be good to go!
Hope this helps!
Rob