ive been wondering the same thing as well. i had a quick look around the map (in ireland) and found these sequences. the image quality is not great though and they dont last long enough to tell whether you would capture that many interesting things
the last time i was on a train i held my phone up for a bit as well to see what it was like and photos were similar enough to the above sequences. slightly blurry and not much to look at apart from fields and trees but you might have better luck if you are going through a lot of towns and cities
ive got a gopro since though s next time ill see whether that does any better for shutter speed
having the camera in the drivers cabin would be ideal… but then you worry about haggling with the driver to let you leave your phone in there or whether you want to trust the driver not to be looking through your txt’s 
