Well, the ghost stuff... Right now it isn't clear if the creator committed sweesede or not, but I can guarantee that the black figure is just a hoax. I walked around the map for about and hour with an aimbot gun, and I didn't find anything! The rails? Nope. The hotel? Nope! The entirety of the sewers? NOT. A. THING! This entire rumor is a hoax like the "Demon Door" thing we all used to do as young and naive children. The longer you're sweating on your keyboard and mouse waiting for Herobrine, the more paranoid you become, and so your mind starts playing tricks on you. (Don't do this because it's scary, but...) Go to your bathroom or the nearest mirror. Do your best to dim the lights to just where you can barely make out your facial features in the dimmest possible setting. Now stare. Stare and wait. Your face got disgusting and terrifying, didn't it? That's what I think happens here. These people claim they saw the figure, but in reality, the game didn't even show anything. My theory might be completely wrong, so correct me if I am, but until I see this 'ghost figure' in photographic or mp4 evidence...

Thank you for coming to my extensive Ted Talk.
I'm sorry if I sound Karen-y or if I'm completely wrong.

Updates:
1. This thread got in a video!
2. Many others have rooted through the files for the map, I suggest you go check them out.
3. This was written really poorly since it was really late. The TL;DR is that I went throughout the map with an aimbot gun which will instantly lock onto any NPC entities (including players, friendly NPCs, enemies etc.). If there was a ghost, monster etc., I guarantee that gun would lock onto it. Plus people have gone through every sound, ambience, texture, model and script.
No ghost.