these two paramilitary guys -with their bags full of weapons/sattelite radios?-, the stories about sniffing dogs and cops announcing a drill right before the blasts...is it possible that authorities knew something was going to happen, attempted to stop the perpetrators sending guys on the scene but arrived some moments only too late ?
That is a very plausible opinion. I'm sure they keep all types of security procedures quiet and out of the eyes of the public. They certainly might of gotten a late warning about some sort of attack, and just couldn't get the jump on it. Now they are keeping mum about it to avoid figure pointing, lawsuits, etc.....
You'd also have to worry about stampedes, the spectre of an early detonation, etc.... if you were to show up and preform a quick police evacuation.