Over the last couple of weeks I have had a few people letting me know that federation is broken, as they can’t see the status of a federated user.
After some investigation I have found that federation is working as expected, the “issue” (not that it’s an issue) is the way that Lync displays status information for federated contacts.
When searching for a Lync user’s status within your owncompany status is displayed in the search results.
However until you add the federated contact to your “buddylist” their presence status will be displayed as “presence unknown”
Hover over the contact and select the 
icon, and select which group to make the usera member of from your “buddy list”
icon, and select which group to make the usera member of from your “buddy list”
Once you add the contact to your “buddy list”
The status will now be displayed for this federated contact when you are searching by SIP URI.
[UPDATE: Spotted some spelling mistakes]
[UPDATE: Spotted some spelling mistakes]
