I have the same problem with mouse84's version of the PO&N route, which is for Trainz 3.4, the MP version. So it is highly probable that -3:12000 is a MP version of the portal, and I don't have this version. Won't, because the MP version does not support compatibility mode any more. I'll wait until the next Trainz version comes out which does not overwrite TS2010 SP3 so I can have both versions in parallel, compatibility mode and MP, although not at the same time. (I can live withouth scenarios, although.)
Dralex
I have a version of trainz that is patched to 44088 wheich is not multiplayer
then i have another trainz on my hardrive that is patched to mulit-player you can have teh best of each worlds