Ceramic tooling is used for some injection molded plastic kits that are
commercially available in both HO and N Scale.
I've heard that the Beyers (???) horses are molded from ceramic molds made
by the same company that supplies tooling
to a couple of manufacturers that make those kits.
The finish and fit of the molds can be pretty good..... although AFAIK
ceramic tooling has not been used for rolling stock.
The tooling isn't good for large numbers of shots, but certainly enough for
one-railroad prototype freight cars of specialized
interest. And if you guess wrong new inserts can always be made to replace
the worn-out ones for a fraction of the cost
of having a damaged aluminum or steel insert repaired or replaced.
Railroad Model Resources