There were definitely two cameras in use on different riders. In some scenes you catch glimpses of brake levers and you can tell when the rider is standing to pedal from the way the picture tilts from side to side that this camera is mounted to the bike. The other camera is helmet-mounted (I think on the lead rider) as you can see it on the rider's shadow. Obviously the turn to the right that you mentioned was a quick glance to the rear by the helmet-camera rider.