the lights you see are the floodlights for filming, the lights on the skier are flashes set up for the photographer. Most likeley it was a 1/4 or longer second exporsure so you get some of the backgroundwith a strong flash at the beginning of the exposure to freeze the image of the skier you see. That's how most urban night photos like that are done, to the best of my knowlege (If there's a better way, someone please elaborate)