ha! well that's first i've heard that... sounds pretty far fetched. bull, pine, and gopher snakes are nothing like the rest of Elaphe/Pantherophis to me.
i know the original study was not approved, but a friend of mine had told me that the follow up is taken to be fact now; and since he's a herpetologist and a teacher at a major university i figure he knows what he's talking about.