Search for the JbpmCallback, he basically does what you need (if you have all correlation properties still on the ESB message). Best is to use this and maybe have an additional action setting the properties if yoiu "lost" them.
But the whole integration is not powerful enough and serves only the basic correlation use cases, so in real projects we always had to extend the machinsms there (and by now I think it would be easier to rewrite the jBPM/ESB integration completly ;-)).
Unfortunately direct use of the signal command within jBPM 3 will fail very quickly once you move away from the simple scenarios, which is why we jump through those hoops. This was fed back to the jBPM team and they are supposed to be addressing this.
The present integration focusses on interactions between ESB services and jBPM, forcing a 'one time only' execution of the signal. The EPR contains additional information necessary to enforce that guarantee, i.e. one request and one response.
I would be interested to hear about any other scenarios you are facing, especially those in which you feel the integration falls short. What additional integration features have you had to add? What were the reasons behind those?