Looking at the artist's webpage[0], you can find videos[1] of the work as well as different angles. The before/after effect does look fake, though. I think you are right that the before picture is the one being photoshopped.

[0] http://www.a-fresco.com/pages/ville.html [1] http://www.a-fresco.com/video/video_recre.html

True, I hadn't thought of that!