I don't know if JBPM-3319 will be fixed (it's a big issue form me, since I don't know how to manage a aborted workitem situations without a subprocess). Anyway, looking at the code, when a WorkItemManager.abortWorkItem is esecuted, an event is sent to the process instance:
processInstance.signalEvent("workItemAborted", workItem);
So when (and if...) the boundary events for the task will be supported, it should work simply with a "catch" event from the task.
Am I wrong?