I just noticed that even though I get this exception, I can still login and access JBPM console. But I would still like to understand what I am missing here.
This is most likely due to a different deployment structure (and also an open JIRA task, see JBPM-836). I suppose you have jbpm-enterprise.ear and jbpm-console.war (or your custom jbpm web app) deployed separately, ie not in a nested structure. Deploy the war nested inside the ear and the local reference to TimerServiceBean can be resolved.
Thank you for the reply. Using nested structure fixed the problem.