bus-entensions.xml and extensions.xml files are use when building up the Bus through the ExtensionManagerBus. That scans for all bus-extensions.xml available in the classpath and load configuration fragments from them. Given jbossws-cxf integration does not need to change anything about that, there's no need for duplicating them in jbossws-cxf-client.xml.
We might want to add another one for jbossws additions only.
Btw, this has the side effect of simplifying the cxf upgrade process.