Mine are low-level, but may be good examples of using basswood and aircraft plywood. If you choose the right sticks, you can even size them for ready made sidewalks and roadways, so should work for high-level platforms.
I need to pay more attention to scribing expansion joints, but here's one at Hesperus. I generally use basswood when things will end up square, for exampls the station platform and foundation. For platforms that follow a curve, like the oe here between the tracks, 1/32" aircraft plywood works well. You can use scissors to shape it after cutting a cardboard template to get accurate sizing.
Durango has the most extensive installation.
Mike Lehman
Urbana, IL