It is impossible to do in Moscow, too!
I'm really don’t know how they did it in St. Petersburg, but at events in Moscow there is very strict control, we couldn’t even get carry drinks at Chems gig, what to say about flares.
Perhaps this is even the lack of security at this arena, in this case.
I would imagine they would have shut the show down immediately as a safety risk.
When i was last year at The Prodigy gig, there was an big announcement to not bring the flares, or show will immediately will shut down.
And Maxim Reality shouted every 15 minutes: "No fucking flares, oh my people.."