No, there is no problems. Kato N scale trains are designed to work in a
a standard 0-12VDC operating range. Same as all the other N scale
trains manufactued since the beginning of N scale.
But as Greg mentioned, Kato Unitrak accessories (not the trains
themselves). have an unusual design.
The only other issue I've heard of is that early (non LED based)
lighting units have been known to heat up enough to melt the model's
roof when placed on a DCC track (because DCC supplies more than 12V).
But this is not a problem on any standard N or H0 DC power packs.