There has been some speculation that this nine-minute video, "What's in the Box?", is some sort of teaser for Half-Life. And that makes a lot of sense: the character audio track is "missing"; it's all shot from a first-person perspective; it's set in an empty European city; the sky is yawning open to puke down fireballs over a giant tower. Oh—and it uses Half-Life sound effects.
But it's all far too similar for me to think it's actually something sanctioned by Valve, especially when one of the things that makes the Half-Life series feel like it does is Valve's commitment to making the game experience itself tell the story, not cut scenes or accompanying films.
I'd go along with "Half-Life tribute film"—and it's a very good one, at that.