I stand corrected. Thanks for the post Ralph. It does work indeed. The Server MBean does have an attribute 'pid'
wsadmin>dmgr=AdminControl.completeObjectName("name=dmgr,type=Server,*")
wsadmin>
wsadmin>print dmgr
WebSphere:name=dmgr,process=dmgr,platform=proxy,node=homenetCellManager01,j2eeType=J2EEServer,version=8.5.0.1,type=Server,mbeanIdentifier=cells/Cell01/nodes/homenetCellManager01/servers/dmgr/server.xml#Server_1,cell=Cell01,spec=1.0,processType=DeploymentManager
wsadmin>
wsadmin>print AdminControl.getAttribute(dmgr,'pid')
2677
wsadmin>