My guess? It could be a hoax, or it could be that the video recorder is re-using old videotapes. The recorder isn’t completely writing-over and old recording, so an old image is bleeding-through the new one. (Kind of like if you record over an old cassette tape and the old recording is still faintly audible in the background.) The fact that the video-cameras don’t move would also help everything align correctly in the old and new recordings.
Then again, I just looked up the Disney Haunted Mansion attraction, and the fact that the “ghost” is leaving the Haunted Mansion makes me think this was faked by Disney to add to the mystique.