Mule 1.4 comes with an BPM Connector. This connector can integrate with BPM engines that provide a Java API. If there is a requirement to integrate with a BPEL engine standard web services with the soap transport (axis/xfire) canbe used.
jBPM is the first BPM engine that comes out of the box with Mule 1.4.
It looks pretty cool. You can easily write your long running integration processes in JPDL.
I hope to see integration support for JBossRules (Drools) engine in the future.