Confirmed for "The eleventh hour" rush. It is possible to go even faster. Just clean the first area using shotgun and switch when out of ammo without reloading. In the second area, you can run through the train to avoid the smoke and take ennemies on the flank. One guy finishes the room when the second one rushes the last area to activate the bomb.

That's really fast...

I haven't tried this AA thing because I unlocked everything already.