To migrate UM contact objects from Lync 2010 to Lync 2013 is very easy – one line of PowerShell easy!
Get-CsExUmContact -Filter {RegistrarPool -eq “pool01.domain.com”} | Move-CsExUmContact -Target pool02.domain.com
Microsoft’s migration documentation actually misses this step, so hopefully this will save you some time recreating them all on your new Lync 2013 pool. Unfortunately for me I found this after the fact!
