I've got a bunch of the Blue "Tomica" tracked stuff for my kid. It predates the Trackmaster track, but the scale, engines and couplings are the same. It's actually a Japanese toy line that has been made for quite a few decades and is still in production over there. You can order some amazing looking trains from Japan via Hobbylink or Hobby Search.
Anyway, the scale is much closer to 20mm or even 15mm for many of the modern trains. However, the compressed nature of the cars lends itself very well to the cramped confines of the wargaming table and some are quite detailed. The exception to the scale is that some of the gondolas make great mining cars or even small vintage narrow gauge gondolas in 28mm. I think I've seen some used in this way, but I can't recall where. Last I checked you could get a pack of 3 gondolas for about $10 bucks.
I'm not using any in my wargaming -preferring to go with toys more close to 28mm- but I'm toying with the idea of building a small LEGO layout with Tomica/Tomy/Trackmaster trains scaled to the little one-piece figures that come in LEGO boardgames (around 20mm or so). They're alot cheaper than a vintage LEGO monorail.