I reviewed JSR 250 but didn't find relevant information but I found it in EJB 3.1 spec.
Copy/paste from EJB 3.1 spec. - 16.2 Enterprise Bean’s Environment as a JNDI Naming Context
The container must make an enterprise bean’s environment available to any interceptor class
and any JAX-WS message handler for the bean as well. The interceptor and web service han-
dler classes for an enterprise bean share that bean’s environment.
IOW JBossWS implementation is correct in terms it's trying to access EJB 3 specific JNDI context.