OK, let's just separate what we know from what we don't.
The light trails are caused by a long exposure ( > 1sec.) on the camera. The camera was moved during the exposure.
- The operator presses the button.
- The software senses the darkness, and determines that a long exposure is best.
- It opens the shutter and then very shortly after, the flash goes off. The flash is VERY fast, freezing the foreground subject in the (bluish) light of the flash.
- The shutter stays open, capturing the background lights in a spot in the image.
- The operator then lowers the camera while the shutter is still open, causing the lights to (jerkily) zip off the top of the image.
If there had been more than two lights in the background, they would have all had the exact same trails.
This is VERY common in night photography. I worked in the industry for ten years and processed a million of these.
Here are some examples I Googled:
http://pixoftoronto.com/cavalblueXmas.jpg"
http://www.amateursnapper.com/images/car-night-trails-2.jpg"
http://www.digitalimagemakerworld.com/gallery/main.php/d/839-2/DIMi.JPG"
The only thing we don't know is the source of the two lights.