How can I reference the Overridden Default DataSource specified in the managed server configuration?

Referencing java:comp/DefaultDataSource in the context lookup is still returning the built-in Derby datasource.

I would expect these two statements to be equivalent (with the managed server default datasource (image attached) set to: jdbc/CommunicationRoutingService )

1. ic = new InitialContext();
    DataSource dataSource = (DataSource) ic.lookup("jdbc/CommunicationRoutingService");

2. ic = new InitialContext();
    DataSource dataSource = (DataSource) ic.lookup("java:comp/DefaultDataSource");

The 1st works correctly, the 2nd returns the Derby datasource.

I'm curious if anyone has gotten this to work.

Thanks