The protagonist is a modern person, and the train is from Victorian times. It has a lot of cadavers in it, which the protagonist perceives as large bags. It is buried under ground, which is implied to have happened quite a while ago; probably when the train weren't buried. The guy said the train's destination was some kind of island, but I don't think that is literally the case, since the ghosts seems to be unfamiliar with that place. I think that is the place they intended to move the train before it was buried again. The protagonist is some kind of archeologist or paleontologist who was called to examine the buried train, but was caved himself. When he woke up, his mind created a fabrication that he was on a train to... the train and that it was still moving; because he really didn't need to panic and use up all the oxygen. His mind replaced the bodies, either with a bag or a "ghost". They are all probably an invention of his mind, but I still think there is some actual "ghostness" to them.
There is probably more, but I can't think of anything else at the moment.
I soiled my trousers every time a monster didn't jump out of a closet and shout "boo"