Hey Phil, I seen your question and I needed something similar to check nodes results. What came after was to use a Decorator which can report back the results of the node its attached to once the node finishes execution. This event within the Decorator is called the Event Receive Execution Finish, returns Node Result enum which you can Switch on. The enum breaks down 4 different states; Succeeded, Failed, Aborted, or In Progress.
So I have a decorator on a node which tells the AI to move to the next route(increment bbdata int route up) if it finishes it current route successfully. If it aborts in your case, it can call functions which do your garbage collection.
I hope that is what you’re looking for. 