I'm getting a bit of an education, I have to say. Anyways, the miscreants are well below the Mafia when it comes to covering their tracks. (This time, anyway.) Should this scandal lead to a prosecution, I'm sure that a capable prosecutor will have enough evidence to make the case without reliance upon the leaked documents. I'm sure you know how Al Capone was turned into a convicted criminal.
And it's interesting to me that the senders and the receivers seem to have acknowledged authorship/receipt/authenticity, that might constitute an admission.
But of course if there are enough 'real' scientists left to raise a ruckus, these folks are through in the field, regardless of the legal consequences.