When people say they have trouble looking for rail booking info, I'm surprised no one has mentioned
www.seat61.com. This is one of the most informative sites in existence about rail travel abroad.
You can tell that the guy who founded the site has genuine rail enthusiast knowledge by the name "Seat 61", this being one of the few seat numbers in Eurostar coaches where you get a window with a view unobstructed by pillars and other things!
I'd be interested to see the research, although I guess the answer might be that it's confidential for some reason?
I wonder what this research took into account? For example you could argue that no-one in their right mind would transit the Atlantic by ship when this takes at least 6 days, when a flight can do it in 7 hours, yet Cunard (and others) manage to fill their transatlantic ships with literally thousands of passengers.
It makes no sense to take journeys of over 24 hours in the USA by train when they have more flights than anywhere else in the world, yet Amtrak have plenty of sleeper services which fill up nicely.
Why on earth would people want to take a ferry across the Channel taking 90 minutes, when the Eurostar takes just 30, but P&O and DFDS think it's worth carrying passengers. Enough to justify running quite big ships many times every day, and that's before we even start on Stena and Brittany which happily fill their overnight berths all the time despite taking far, far longer than competing flights do. Even though they often rock around a lot more than trains do.
So really, it depends how you look at it. I'd certainly enjoy an overnight rail trip from London to somewhere in Europe over 500 miles away, and ideally from Manchester or Birmingham if that possibility hadn't been scuppered, and I suspect I'm far from alone. The odd thing is, there seems to be more people on the rail forums that are ready to rubbish these ideas than there are in the outside world. Strange!