After cruising fields and strats with God's Eye View, I was unable to fly through any buildings per se. However, I WAS able to go through some "structure" objects. These look like small hills but I know they're "structures" because I've blown them up, both with bombs and with Destroy Objects.
The hill "structures" I was most able to penetrate were at airfield towns. At each town, I was only able to go through the hill closest to the airfield, which did not have the water tower on it. The other hills at the same town, and the hills at airfields that the control towers sit on, were solid. Once I got inside the hill at the town, it was invisible and I could see the buildings on it hovering up in the air. I was then able to move into these buildings from underneath and out through their roofs and walls, but could not go back through them again from the outside.
The other hills I was able to enter were at the refineries. I could not, however, go through the hills at the ammo factory. I didn't have time to check other strat factories.
