GERONIMO-4559 "fixed" our JMX processing so that, by default, the Geronimo server will use the Platform MBean Server, rather than creating a Geronimo unique server. This means that JVM and Geronimo (and embedded technologies) can all be managed using a connection to a single MBean Server.
IMO, our current behavior is broken/difficult to work with. I think this should be "fixed" in 2.1. Likely that managing a single connection is more secure (or at least consistent).