In Lync Server 2010 the way to assign a default dial plan/location profile to a Mediation Server is to create a CsDialPlan and use the service tag with the name of the corresponding PstnGateway Service, i.e. New-CsDialPlan service:co1-PstnGateway-1 –name co1-PstnGateway-1. On restart of the mediation service you’ll see it pick up the new dial plan in the event log (25029).