When installing jbossas together with cxf (jbossas-ws-cxf) there are some additional files compared to zip distribution with cxf installed:

server/production/deployers/jbossws.deployer/jaxrpc-api.jar
server/production/deployers/jbossws.deployer/saaj-impl.jar

The same applies for all, standard, web and default server profiles.

These files are not present when you install cxf on top of the zip distribution.