With the 11g release of OSB EJB3 is supported in the EJB SB transport. Now you can use all your Remote EJB's of your Model Tier. This is not all, Oracle also added a new Transport called JEJB. This works almost the same, only now you are passing Plain Old Java Objects (POJOs) through the Service Bus. With the EJB transport the Java Web Services (JWS) framework is used ( easy for transformations ).
With JEBJ you can also use a Java Interface in a Proxy Service and expose this Proxy Service as a Remote EJB. So you can remove the existing EJB and replaced it with this Proxy Service. Or add some logging or java transformations between the Proxy Service and the original EJB in the Business Service. When you are not using a JEJB Business Service for this Proxy Service then you need to add a java callout in the response and return the right POJO. Soa Suite 11g also has this feature to expose a service as a EJB.
So lets give it a testdrive.
If your remote EJB is running on a different J2EE Server then you need to add a JNDI provider for your EJB or JEJB Business Services.
Create a Business Service with a Transport Service Type.
The JEJB Transport works the same, only now, plain java object are transfered. Select JEJB as protocol and as Endpoint URI jejb:JNDIModelTier:XXXXX , JNDIModelTier is your JNDI provider and XXXX is the JNDI name of your remote EJB.