They will DEFINITELY run into trouble with Apple's app store policy. Apple doesn't outright ban apps that do this but they have to clearly state what they do when requesting location services permissions. There is a string called "app explanation" that has to state what they will use it for. Theirs says:

"Find Theaters and movies near you, and be able to use the app to get tickets and the theaters."[1]

There's nothing about tracking you outside of that purpose. Nothing about your drive to the theater, nothing about where you go after. So if they're doing that or start doing that, they should and probably will get kicked out of the app store.

Having said that, I wonder if this is true for their iOS version or just Android. The privacy policy in their TOS is probably sufficiently vague to pass legal muster.[2]

[1] On iOS go to Settings > Location Services > MoviePass

[2] "we ask you to supply us with personal information so that we can provide, enhance and personalize our services and marketing efforts" https://www.moviepass.com/privacy/