FSX still overlays the terrain with 3d objects. One of the limitations of the tileproxy is that it is completely flat 2d, witht he 3d objects on top of it. It actually looks best with autogen scenery disabled. So basically if you fly under a bridge, you would fly under the 3d object, yet over the "texture" of the bridge as seen by the satellite.
Forgive my spelling and grammer, I am on percocets again.. another stinkin kidney stone.
Sol