Using JBoss AS 4.2.3 and JBoss Cache 1.4.1

I have 4 servers.  3 are clustered together to host a web application.  The 4th is a dedicated EJB to process batch requests from the three other servers.  I need the 4th server to be able to access the cache that is used/modified by the web app on the other servers.

The admin is telling me that if he adds the 4th server to the cluster, then the EJB will be put on the other 3 machines and the web app will be put on the EJB server.  I don't want this.  I've been trying to find a way for the EJB to access the cache without having to join the cluster.  I've creating a second cluster to host the EJB and tweaked the replSync-service.xml on both so that they are the same, but I can't get them to share the cache.

I've tried to find doc on this, but have been unable to do so.

So my two questions are: Can the cache replicate across clusters?  If not, can the cluster be configured so that 3 nodes have only the web app and the 4th node has only the EJB.

Thanks in advance.