I don't know about Tibco, but if you end up having to implement something, there is an example of an integration of JBossMQ with oracle's AdvancedQueueing/JMS in the jboss patch 912173 (see link below).
I wouldn't take this example as a good example of an implementation since it does some nasty stuff with inheriting from some internal oracle classes, but it does work OK.
I don't known anything about Tibco, but integrating JBossMQ with Joram I found a lot of answers in these Wiki pages:
Finally, having a look to the default JMS config files can help as well (located in JBoss/server/default/deploy/jms )
The " TIBCO Enterprise Message Service Application Integration Guide" section of the Tibco documentation shows how to integrate Tibco EMS with JBoss so you can have MDB's consume messages from a Tibco destination. This isn't quite a 'bridge' though it looks like something like that might be on the TODO list:
If you ask Tibco Support, they can provide you with a document that walks you through step by step integration with JBoss.