Just arrived after spending 28 hours on the train. Great experience so far, one word: Ivan. More on that later, if we finally manage to get mobile Internet set up on the next train. And if Sputnik doesn’t wobble again, other story, relates to Ivan.
Quick photo of a sign on the train though:

My Russian still sucks, but from the picture I was guessing that if there’s a fire in your cabin, your Waggon gets disconnected and you are left to burn to death.
Bottom line: Do NOT start a fire in your cabin!