This will list all used phone numbers in Lync. Except those used by Exchange UM (Auto Attendant ..)

$LUser=Get-csuser -Filter {LineURI -ne $Null}
$PLUser=Get-CsUser -Filter {PrivateLine -ne $Null}
$LCommonarea=Get-cscommonareaphone -Filter {LineURI -ne $Null}
$LAnaloge=Get-csanalogdevice -Filter {LineURI -ne $Null}
$LAppEndPoint=Get-CSApplicationEndPoint -Filter {LineURI -ne $Null}
$LExchUM=Get-CsExUmContact -Filter {LineURI -ne $Null}
$LDialIN=Get-CsDialInConferencingAccessNumber -Filter {LineURI -ne $Null}
$Workflow=Get-CsRgsWorkflow
$LDevices=$LDialIN+$PLUser+$LUser+$LCommonarea+$LAnaloge+$LAppEndPoint
$LDevices|sort-object -property Lineuri | ft DisplayName,LineUri

This is how I’ve done it. First in lab then in production. This is moving enterprise edition databases. For this to work you need one extra temporary sql server and one Lync server in a temporary Lync pool ,along with the new SQL production server.