Actually, Fantasmic is a "The show must go on." kind of show. So if either Steamboat Willie (Hollywood) or Mark Twain (Land) malfunction or are out for servicing, the stage finale occurs instead. This and other contingencies can be found here: ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-dKZvJuEzHno.html
They only did that because the Mark Twain boat was being refurbished ... Fantasmjc has all sorts of alternate scenes for when something goes wrong or isn’t working at the time of the performance , it’s pretty cool how they work the show