I feel like you've answered your own question but maybe I'm missing something...Android 5.0+ exclusively uses ART so if the app doesn't work on ART then it won't work on this ROM. That being said, it's up to the app's developer to build in support for ART. Otherwise you'll have to stay with kitkat or lower to run the app on dalvik
The game added Android Lolipop compatibility. The unofficial Cyanogenmod 12 thread in this sub section works fine with the game. So I'm assuming it's this ROM.