The blog post if from 2009, so I will not count on that.
We are now about to release jbpm 6.1 and to be honest the best way to migrate is to redesign your workflows to fit the bpmn2 spec.
Going for an automatic migration path will be confusing and error prone.
My issue is that the workflow we have to migrate has similarities with the cases described in jbpm6.1 doc : Chapter 23. Flexible Processes
The humans involved in the process are able to chose between differents paths for the next step.
But this documentation chapter is not very clear if it's feasible with jbpm 6.1.