I do not own the game, so I am looking for some insight here.

I will be heading to Roseville MN this coming weekend for Arkham Nights where Streets of Arkham will be pre released. I plan on getting my friend a copy (he owns MoM2E) so we can spend Friday night playing the new expansion. In his preparations, he became worried that the app might not let him download the new scenarios which is making us both wonder how exactly the release of those typically work. Does the app get an update when the expansion is released? I sure hope FFG has the foresight to make it possible to play these scenarios when it's released early at Arkham Nights.

Better shoot an email (or call) customer service and ask them directly, here you'll receive just some educated guesses (the situation is unprecedented, to my knowledge)