> Furthermore, the result is impossible to believe given previous results in open elections.
A natural or man-made disaster during a vote filters out the less "passionate" portion of the electorate; if you don't care that much about an election's outcome, a thunderstorm or the threat of riot police cracking open your skull would probably convince you to stay home rather than visit your polling place.
I would imagine the bulk of the "passion" on this topic would reside with the separatists, so it stands to reason the police action ironically resulted in suppressing the "remain" vote.