Its hit or miss. The issue isnt the center rail, its the depth of the flangeways vs the height of the flanges on the engine. You can end up with the wheels not making contact with the rails, and you have no ground.
The same issue happens with some cars... some will ride up on their flanges, while others have shallow enough flanges to ride on the rails. Running with 2 rail cars actually has some benefit here.
I know a guy who runs MTH switchers through super streets and they're pretty cooperative. I suspect most modern stuff is ok, the issue may be with some of the older items that have really large "pizza cutter" type flanges on the wheels.
