Yes, and I'm pretty sure Russia could do that too - if they were getting Blitzkrieged by some outside enemy force. Here, it was a theoretically friendly and small force, that suddenly turned around and drove towards Moscow. Given how much damage blowing up bridges and highways would do to the country, and somewhat unclear threat from the approaching mercenaries, I don't think anyone on the defense side considered dropping a bridge on the highway to be a reasonable move.