BMT doesn't work this way.
The container will suspend the current transaction before
invoking the method on your BMT Bean.
By definition the container cannot provide a BMT Bean
with a transaction, it creates its own.
One exception to this rule is where a stateful session
exits a method without committing. The next invocation
on the stateful session will be with the uncommitted transaction.
Its all in the spec.
You must use CMT for entity beans.