As far as I know, Unitrack uses the standard code100 track, which means all trains should be fine running on Unitrack. In the Netherlands though, it's probably easier to get similar roadbed track from Roco or Trix for example, although it might be more expensive.
If you want good looking track, check out Tillig's H0 track. It doesn't have a roadbed though, and requires some work setting up, so it's only for static layouts.
Why do you want to use Unitrack btw? Japanese trains run fine on other track as well, as long as you keep the minimum radius in mind.
Martijn, HO Unitrak is Code 80 (HO and N Unitrak use the same rail...).
My LHS has HO Unitrak in stock and it looks very attractive, the limited range is a pity though.
Cheers NB