Some observations on what has been said so far - Clearly, having "Cheer" on their blouses seems odd, but... it is more like having a blouse/shirt with "Eddie Bauer" or "YSL" on it - English letters are still very sexy in Japan - it really doesn't matter what it says.
Second, schools in Japan rarely have indoor gyms and their attached locker rooms. Most typically, the students change into their gym outfits in the classroom - almost always, one sex at a time, but the stories of guys peeping or setting up miniature cameras are legion and a common theme in Japanese manga. This means that at away games (usually baseball which has cheer leaders) the teams generally change their clothes outdoors, generally hidden from view. There are (or at least used to be) a number of magazines devoted to publishing pictures of these young ladies changing - much the way the supermarket tabloids here publish pictures of celebrities.
So, I cannot say for certain if the video is legit, but it is well within the realm of possibility that it is.
Cheers
Nanpa
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