In Dune the Emperor has doesn't seem to know anything about OM, surely he would have been briefed on the possibility at some point if anything was known or guessed.
Dune wrote:"You don't understand. Majesty," the old woman said. "Not telepathy. She's
in my mind. She's like the ones before me, the ones who gave me their memories.
She stands in my mind! She cannot be there, but she is!"
"What others?" the Emperor demanded. "What's this nonsense?"
The old woman straightened, lowered her pointing hand. "I've said too much,
It's unlikely BG would disseminate/publish large amounts of historical data unless it served their purposes - bits and bats would inevitably get out, but they wouldn't risk disclosing their sources by being too open about it.
The Ghengis Khan passage from DM, that Lundse mentioned.
Dune Messiah; Ch. 8 wrote:"How much history do you know?" Paul mused aloud, studying the shadowy
figure beside him.
"M'Lord, I can name every world our people touched in their migrations. I
know the reaches of Imperial . . ."
"The Golden Age of Earth, have you ever studied that?"
"Earth? Golden Age?" Stilgar was irritated and puzzled. Why would Paul wish
to discuss myths from the dawn of time? Stilgar's mind still felt crammed with
Zabulon data --
"Stilgar," Paul said, "you urgently need a sense of balance which can come
only from an understanding of long-term effects. What little information we have
about the old times, the pittance of data which the Butlerians left us, Korba
has brought it for you. Start with the Genghis Khan."
"Ghengis . . . Khan? Was he of the Sardaukar, m'Lord?"
"Oh, long before that. He killed . . . perhaps four million."
"He must've had formidable weaponry to kill that many, Sire. Lasbeams,
perhaps, or . . ."
"He didn't kill them himself, Stil. He killed the way I kill, by sending out
his legions. There's another emperor I want you to note in passing -- a Hitler.
He killed more than six million. Pretty good for those days."
"Killed . . . by his legions?" Stilgar asked.
"Not very impressive statistics, m'Lord."
Does this suggest that books were transferred onto electronic formats prior to the Butlerian Jihad, and the files (or the computers needed to read the files) were lost?
The wording also suggests that these are known historical facts - not from Paul's OM. So data does survive from our times. I don't think it's a huge leap that the Baron knew what he was talking about. He was educated.