You need the shader set to Ultra to enable PBR textures, otherwise PBR textures will act like non-PBR textures. Also, PBR textures are all Trainz-build 4.6 and higher. You can use the search filter to filter out all the non-PBR textures and be left with only the PBR textures by adding the filter "Trainz-build" "4.6" (quotations removed).