Here's what I found on the video (some details from Win Butler, Arcade Fire's lead):
“It’s not a video. It’s a short film; we’re still working on it. It’s like a science-fiction B-movie companion piece for the record. Basically, we played Spike some music from the album and the first images that came to his mind had the same feeling as this idea for a science fiction film I had when I was younger. My brother and I and Spike wrote it together, which was really fun– it was like total amateur hour. We shot it in Austin and a lot of kids are in the film, and it was great just hanging out with these 15-year-olds for a week and writing down all the funny things they said. It was cool to revert to being a 15-year-old for a little while."