Further testing has revealed that that the @TransactionTimeout can NOT be used to extend the timeout configured in "jboss-service.xml". However it can be used to restrict it. Furthermore the @TransactionTimeout at the class level works globally and in conjunction with the method level annotation as expected. This mean that we can open up the transaction window to accommodate the longest expected transaction server wide and explicitly configure reasonable timeout windows at the EJB component level. With this approach we will be able to open up the transaction window for specific operations up to the max server defined timeout.
In our initial testing it appeared as if the TransactionTimeout annotation was not honored. Now it's clear that it is honored and can be used to limit the server default but, it can not be used to open it up.