AT&T launched a new UC Federation service that connects across disparate unified communications (UC) systems, including Microsoft Lync and Cisco Jabber.
Key capabilities include:
- Connect to supported UC platforms of partners, suppliers and vendors
- Control which organizations can communicate at the company, group or user level
- Allow communication methods (like instant messaging) and block others (such as online presence).

Sonus has deployed and trialed AT&T UC Federation and is in the process of a full service rollout.
AT&T said it plans to extend UC Federation beyond IM and presence to include calendar integration and video and voice capabilities later this year. Additional UC platforms may also be supported in the future.
http://www.business.att.com/enterprise/Service/unified-communications/uc-as-a-service/uc-federation