while it is good it use tvs diodes for voltage spikes ,be aware you can use them anywhere you want and as many as you want but when you get a shorted tvs diode the more you have installed the longer it will take to find for instance which one of the 30 tvs diodes you may have installed all over your layout and possibly if you installed them inside each engine! at least if its only in the engine you can try another engine on the same track and find out it was the other engine and not your layout!
not putting the tvs diodes down there great protection but when they fail shorted it will take time to find which one or how many went bad!
Alan