Couple of scenarios presented to us recently:
Can you assign multiple DDI's to the same user and have voicemails, missed call notifications etc delivered to the same UM mailbox (many DDI's - 1 mailbox)?
Can a user on occasion forward their calls to a common area Lync phone and, if calls go unanswered, have voicemail delivered to their personal mailbox / Lync client rather than any associated with the common area phone?