Most of the rinks block school hockey practice sessions, too. The programs are allowed to ask them to.
I have noticed that it pays to wait for games at Alpha. For games that start between half hours, like 9:10 PM, for instance, it's not at all uncommon for it to still be locked at 9:00 but unlock a minute or two before game time, or even shortly after the game starts. It's frustrating but if you keep trying you'll often get in to watch the games after all.