See if http://www.jboss.com/index.html?module=bb&op=viewtopic&t=97309 is any help.
The answer depends on what you need to do. I see three possibilities:
If you just need to get some data from jBPM, you could load it up earlier.
If you don't need to use the same context object, you can create another on the listener thread.
If you need to use the same context object, you'll need to push the work onto the same thread somehow - probably set up a worker thread just for that.
I haven't done any of this stuff - if anyone knows better, please shout!