I would guess not. Terrorist generally don't send phony props or dummy bombs. They want full impact, horrific events causing high death counts etc..
Btw, since these were all involving high profile people, whoever transported the props to the drop points will very likely be on multiple videos. Not to mention the physical evidence involved.
My guess is they'll have a suspect/suspects ID'd and hooked up soon. Of course whoever the suspect/suspects are, it's going to be blockbuster news, with everyone wanting to know who the person/persons are...And will we get the truth?
Are we going to get seven more Seth Riches out of this?
(dead curriers)