I like the idea of putting up a thin view block between the areas as someone suggested with a masonite panel. I would offset it to the yard side and put a bunch of backdrop buildings on the yard side representing the rears of buildings that might face a yard.
Then on the other side where the Mainline is I would put in a lot of shrubbery and brush and skinny trees to create a rural look. If the backdrop is offset toward the yard side, this leaves more room for scenery on the main line side.
Unfortunately this idea makes more sense if you got up 10-12 inches or more rather than 5-6. If you want to stick with the lower height, the wall of trees may be the best idea.
