It's fan made. It is made by a guy named Thibaut Niels and one named Tim Smit. It's for the sake of fun. They were not hired by VALVe, but they are big fans. The video was shot in the city of Nijmegen, The Netherlands, from which my house is five miles. It was shot both on the Radboud university campus and the industrial district. Thibaut Niels got approached by several movie companies, including a lot from Hollywood, asking how he managed to get such high standard effects in what was practically a movie made by one man.
/thread.