Is there a way to get Overlap or Hit Events with Flex Actors like a flex fluid?

Clearly there must be a method for doing this as they do it in the VR Funhouse demo with the clowns that “eat” the liquid and grow the balloon.

But it seems that overlap and hit events are not working so how can I detect particles within a volume and then delete them (while getting the count for how many are deleted)

So how is this possible?