IMO, this can be done on the same layout because of forced perspective.
The classic station (at least O Scale, maybe Standard Gauge) with O Scale trees in the foreground, with an HO theater and HO buildings in the background, on my O Gauge layout.
This forced perspective is not limited to HO and O Scale. If the layout is deeper than mine, it may be possible to put N Scale structures behind the HO structures, which are behind the O Scale structures on the same O Gauge layout.
Now, you can share photos and explain how you may have combined different scales of structures on your layout. Arnold