Property Broker actions ultimately inherit from org.eclipse.core.commands.IHandler. The object sent into the execute() method is an ExecutionEvent object and we use the trigger to house the PropertyChangeEvent. You can get the full view id of both the target and source by inspecting the Wire contained in the PropertyChangeEvent object.
PropertyChangeEvent pce = (PropertyChangeEvent) event.getTrigger();
String sourceViewId = pce.getWireDefinition().getSourceEntityId();
String targetViewId = pce.getWireDefinition().getTargetEntityId();
You can now use those id's to locate the actual view parts using the SWTHelper class in the package com.ibm.rcp.propertybroker.swt.
IViewPart sourceView = SWTHelper.locateView( sourceViewId );
IViewPart targetView = SWTHelper.locateView( targetViewId );
Locate View not only searches the current page but also any page within the composite application and it will change perspectives if the view is on another page within the application. The method also searches the side bar area for the view part. You can learn more about these API's on the Lotus Expeditor InfoCenter