MBeanServerFactory.findMBeanServer(String); requires the MBeanServerId attribute of its delegate MBean, which I don't think is "jboss".
It's more likely something built at runtime and specific to the process running JBoss.
Your suggestion applies to the MBeanServer.getDefaultDomain() though, which can be "jboss".
So I would have to loop through all the MBeanServer returned by the factory, and check the domain.
Does that sound reasonable?