I have a logical answer. If you look during the gameplay and the ensuing cut scene, this was during the absolute beginning of the evacuation, because of all the civilians still in the streets and limited military presense during the fight. Later in the game, these lights should be turned off as the Power Grid is likely to get shut down.
Also, this is the pinger attack, which means it's one of the first levels. The Wall Trailer shows papers saying "lost in Pinger Attack", so this attack must have happened before any real evacuation was able to take place.
I hope this clears things up. I'm surprised nobody connected the dots like I did.