Based upon Wikipedia the stadium is not in Katowice, while it is very close geographically, I too will concur that i'll wait for a more educated opinion on it than mine!
It's just over 200m from the city limit of Katowice, I think it should definitely be accepted, since it obviously mainly serves the population of Katowice, being the largest city in the Metropolis GZM and Upper Silesian metro area.