Well, it runs on the Atlas 54 I have, quite well, with no problems. I cannot testify to whether it handles O-54 switches, which in my experience is always the biggest challenge to a O-xx rated loco: can it handle switches with curve3d portions of that xx diameter? I don't have any switches on my O-54 loop. But it handles 54 curves smoothly.
It looks a bit strange doing so, however - quite a lot of boiler stick out and such and I need wide clearances for buidlings alongside the tracks, etc. because its most extreme point is jutting out past the outer rail quite a bit. I actually prefer to run it only on 72 inch curves where its stick-out looks less extreme. But mine runs on 54, no doubt about it.