We released an update to Mac Communicator (13.1) earlier this week which enables customers to share their desktop from a Mac.  This release includes a huge new feature as well as some important bug fixes for our enterprise users. For the first time, we will support desktop sharing with both Mac and Windows Communicator users.

How do you get it? 13.1 will be delivered to the customer through MAU through Communicator's first updater. Users will need to install MC13.0 and then apply this update. 

http://www.microsoft.com/mac/enterprise/communicator