The SubjectCreatingPolicyInterceptor is used for proper JBossAS<-->Apache CXF authentication integration (JAAS) as when a subject is created, the principal needs to be checked with the JBoss AS security layer.
In some usecases, though, the subject is not currently created by the JBoss security layer after having checked the credentials; in such cases (for instance when using UT as supporting token) Apache WSS4J sets its implementation of principal into the wsse results that are processed by CXF, which in turn sets that into the WebServiceContext (WSS4JInInterceptor::doResults), hence bypassing the JBoss authentication/authorization.
We need to have the SubjectCreatingPolicyInterceptor extended to deal with those usecases too (IOW when there's no CXF UsernameToken attached to the Message, but there's a SecurityContext instead).