In JBossESB, MBeans can be deployed inside of .esb archives. The deployment is pretty much standard and the mbean configuration lives in the jbossesb-service.xml right in the root of the .esb archive. If you need the mbean to be up before the rest of the .esb deployment, then you can reference the mbean in the META-INF/deployment.xml. If the mbean depends on another .esb service archive to be deployed first the you need to add that dependency to the jbossesb-service.xml.
If you're looking for an example check out the jbossesb.esb.