Below is my setup,
Lync front End 2010
Lync Edge 2010
Lync 2010 Mobility
Lync Front End 2013
Lync 2013 Mobility
Microsoft TMG as Reverse proxy
* I have successfully configure Lync 2010 and Lync 2010 in coexistence state.
* I was able to make calls from Lync 2010 to Lync 2013 and vice versa.
* I was able to make calls from Lync mobile App to Lync client internally. (Just for Lync 2013)
* Configure TMG reverse proxy to send web services traffic to the Lync 2010 front end server.
* Also able to access dialin,meet,lyncweb URLs from Public internet.
But I was not able to sign in to Lync 2010 & Lync 2013 server at same from Lync mobile client. As auto discover URL was not able to resolve proper front end server & not able to return to the correct external web services FQDN.
To solve above issue,
1. Login to Lync 2013 Front End server & change Lync 2013 front end server web services URL to lync2013.vmwareandme.com & publish Lync topology.