Okay, took a look at the auditorium, and it does indeed work exactly like community lots. I also took a look at the gallery, and so far I only see 2 replacement builds. But both of those creators have uploaded all 4 versions.
So, for example, the build that they called Lime Stone Auditorium. First, you get the vast, empty version for the first phase. Then, switch the tab to Formal Dance, open the gallery again, and get Lime Stone Formal Dance. You'll just have to do this for each phase. Or, get the empty version, and decorate it yourself for each of the other phases.
And reading your original question again-- Yes, get this all set up, and the auditorium will change for each event on its own. Just randomly visit on a weekday, and you'll see the basic "auditorium" phase. Attend the prom, and you will see it has changed to the Formal Dance phase.