Following on to what seems to be a common gotcha of the presence being unknown for federated users when the users registrar pool is the newly built Lync 2013 environment.
So to break this down for understanding.
You have a Lync 2010 EE pool/Standard Edition with a Lync 2010 Edge estate. While users who are homed on the Lync 2010 topology can continue to federated with external users including seeing their external parties presence status, you are finding the new users who you have moved to the Lync 2013 estate don’t see the external parties presence.?? why?
It seems most people put this down to the certificates between Lync 2010 edge and the Lync 2013 edge which could be the case if you haven’t set you Lync 2013 estate up correctly… Usually this problem is one that is easily overlooked and is a simple fix.
If you open up the topology and navigate to the site level and edit the properties and look at the option (check box) which says Enable SIP Federation. My guess would be you don’t have this checked. Select it then drop down the Edge server from the selection box.
Check this box and the federated presence should start working as expected. (The end Lync 2013 Client User will need to logout and log back into the Lync 2013 client for the presence to start showing)
(its also worth noting that this issue works in reverse of the above example. If you have a Lync 2013 edge topology and you have users homed on Lync 2010. If you don’t check the enable SIP federation then the users registered on Lync 2010 wont see the external parties presence)