pzCanPerformAssignment will check whether user has access to open the instances of pxObjClass or assignClass that has been passed on to ruf.
This rule looks up the assignment page and work page. It then sets parameters containing selected properties from the assignment. Then it calls haveAccess on the work page. If the RARO for that work type specifies an Access When for Perform Assignments access, then that Access When is invoked by the engine.