The DVD commentary indicates that there were surveillance cameras in the locker room.
"The cutting here is very intricate. You know it took some time to get here because we're telling three, four, or five stories at the same time and we're trying to make them inter-related which they are, you know.
"Talking about ownerships here, talking about the stock of each player, there's surveillance cameras...very quiet talking about the bottom line of football, who goes, who stays, injured reserve, so on and so on"
Stone made liberal use of many different camera techniques (such a split screen) in Any Given Sunday, which some critics did not like but he sees no reason not too if it helps him tell the story.
As to why this particular effect was used at this particular time he makes no mention other than the above quote.