Are you sure that is in the specification?
All I can find is this extract: -
Timers are persistent objects. In the event of a container crash, any single-event timers that have expired during the intervening time before container restart must cause the ejbTimeout method to be invoked upon restart. Any interval timers that have expired during the intervening time must cause the ejb-Timeout method to be invoked at least once upon restart.
Which only talks about container crashes not clean shut downs.
Yes, Thats true. Check out this article
Also, few days back i got a reply from Mr Scott from Jboss Inc. He also said the same thing. But still i didn't get the answer that how to configure the timer service with Jboss4.0.
Get the source and look at the org.jboss.ejb.txtimer.EJBTimerServiceImpl class along with the other services defined in the ejb-deployer.xml found in the deploy directory.