Spoke over phone with this. JBMS does this:

EntityManager session = ((EntityManager) ctx
.lookup("java:/EntityManagers/mail"));

And we have JBAOP TX tags. But introspection of the session reveals that the session is the same session for the entire thread. Despite transactional demarcation which of course causes problems for requires new.

Desired behavior is that the EM facade should create different session under the covers and the transaction boundries are crossed regardless of the method of transactional control. (AOP Tx tags in this case)

Please feel free to ask for more info.