Hello Steve (SIRT)
I agree with you --- "less is better" - regarding no need for track super-details in hidden subway tunnels if such cannot readily be seen and thus appreciated. And using stainless steel Gargraves plastic-tie track is a better idea than tin or plain steel track. I believe the older Gargraves with wood ties is originally steel, tin, whatever.
As far as track cleaning --- its the same process and at times, need, for surface R-o-W tracks, Elevated Line Tracks, and subway line (ie" covered) tracks -- the climate environment of the layout and amount of operation with dust and etc. factored in determines all of that.
regards - Joe F