As its name suggests, MR2 is a milestone release and therefore not necessarily as stable as you'd find in a GA. For instance, we've found a few issues with the quickstarts since we released MR2. If you can wait for a few weeks, we're scheduled to produce a GA of 4.2 in July.
The MR2 release had 2 quickstart samples related to jBPM integration:
More are under development but are targeted for the GA release.
We are also working on documentation that discusses BPM & Orchestration in the JBoss ESB.
Can you tell us about your use case? That would give us a better understanding of how we might address your specific interests.