I've heard of methods of spreading the players on the fly, and it looks like one was used in those videos. Basically you bind a single key to do four different movements on four of your chars, one char has the button bound to forward, one to backward, one to left strafe, and one to right strafe, the fifth char has that key unbound. When that key is pressed, they split into the diamond pattern that you see a couple of times in that video, altho the one char that runs backwards is twice as close as the others due to movement penalty when backing up.