In fact then you define timer in your processdefinition it is not executed.
It will be created in special table jbom_timer suring executing of process_instance. . And you should have a schedulerthread running: it will execute timers that are created. To start scheduler thread you can call special servlet which is included into jbpm.war
Koen, the sources are an even better friend. You said:
Just place the file somewhere on the classpath...
But the docs say:
The configuration file can be customized and a modified copy can be placed in the root of the classpath.
The sources say (best docs there are ;-)) say you are right, so maybe it should be 'koen is your friend' :-P