Once you get your head around what the different scales are, and the nomenclature, you'll have a better understanding of what On30 means.
The scales in the picture are named (for no apparent reason) going small-to-large Z, N, HO, S, O, No. 1.
Now, to add to the confusion, those names (HO, for example) only apply to standard gauge trains (that is, "normal" trains that you see every day.
But, some railroads were built with tracks that were not "standard" gauge. Some were narrower.
So now you see scale names (like "O") with a lower-case "n" and a number. The "n" means narrow gauge, and the number is the gauge of the rails in inches.
So On30 is an O-scale model that runs on 30" narrow-gauge track.
So would it run on an HO layout? Sure. On30 track is HO gauge. As long as the clearances were large enough for the bigger model.
Would it make sense? Well, it's your railroad, you can do what you want with it... but it would look about as natural as the Sta-Puft marshmallow man waddling down Park Avenue!