Enterprise Archtiecture Teams role in the Org

Many organisations are having Enterprise Architecture as competency team and many EA teams are playing the advisory role in the organisations in terms of Solution or obtaining prospective customers if it is Service Oriented organisations. Practically speaking EA teams should help delivery units to deliver the services to customers rather than playing advisory or policing role. It should be like "lead by front", but at the same time, EA team is not expected to completely involve in delivery roles. EA team should provide guidance to delivery team by participating in the initial phase and complete the KT, also jump in in critical times.