I know a guy who's a fireman out in PA, and he says it happens a lot. I assume that large cities everywhere have similar stats for something like that. I don't have any hard evidence, but I do know human nature. going to the cooling station involves less effort and risk. therefore it is the more likely option.
Then you've never lived in a city nor played under "the plug" (ask your PA fireman friend) and know little of human nature. It used to get opened in my Philadelphia neighborhood just to screw with the cops who were supposed to be turning them off, it must have been 20 times a day sometimes. No kid is going to choose a "cooling site" over standing in front of an open water main blasting them full force.