There are other lighting glitches in the video too. In the city scene when the soldiers are creeping behind the wall with the sunlight coming through the windows and they step into a beam of light, it looks like their whole body becomes "lit" all at once and goes back to being "shadowed" all at once.
Half Life 2 looks like it will be an amazing game, it just doesn't have the consistent "everything is done the same way" lighting model that Doom III has.