"Offices Complex" : Mc Kinnsi building
1/ inner door at first (ground level) floor can be opened and closed, but not walked through.
2/ rooftop's sheltered exit : not possible to climb past the last stair, and thus to reach rooftop as scheduled.
"Rivertown" :
It is obvious that the map is not polished yet, nevertheless :
1/ left-most red-roof building with kitchen : (some) ground level windows may be walked through (crouching).
2/ largest grocery : there is a box on the ground near the cash register. When an alien stand on it, his head emerge from the ground above ! He is seen and can see. There seems to be some space between the two lower levels, as we can see at the other river's bank from within the groceries.