I originally had something similar to this -- HibernateBundleActivator itself was registered as the PersistenceProvider and provided a custom createContainerEntityManagerFactory(PersistenceUnitInfo, Map).  However, I had to remove it in https://hibernate.atlassian.net/browse/HHH-8053.  Users had quickly complained that there were attempting to use pre-existing persistence.xml files with an explicit persistence provider set to HibernatePersistence.  If that was the case, Aries complained about not finding the provider.  Unless I missed something configurable in the container-managed persistence unit environment, we reverted back to using HibernatePersistence