That once again, belongs to the container where you embedd the framework. If you are looking for fail-over and clustering you should embedd jBPM inside jboss and you will get all those features for free
If you know how to configure jboss in a cluster, everything will work automatically.
Keep in mind that we have multiple faill-over levels.
a) if a application in a clustered application server goes doesn we can ensure application continuity (refer Mauricio's note above)
b) if a physical server goes down, clustered virtual machines can ensure system continuity of the jboss cluster