preetss:
If I understand your question correctly, you have one main number to take message. This # is associated with a group mail box, your question is: How to make all subscribers in the group mail box to recieve the MWI on these members' phone?
You need to go to Unity and look under the mail number's configuration then look into Message Notification tab and configure the member's extension on each additional notification page. I haven't done this before. I hope this is it.
Notification of messages to the user's phone is the function between Unity and Call Manager. So if you have a hunt pilot # with voice mail box and you want to notify multiple Call Manager users. I would look into what I said above. Hope this help!
KC