Here's a little bit of information that I learned not too long ago that can help many. This shows that it is possible to slash the poly level of a object made in Google Sketchup in half for Railworks.
Often what is created inside is a bunch of unneeded hidden faces that we're going to delete.
First, scroll your camera inside of your building so you're looking at the interior of the building.
Next, we need to select our Point/Edge/Face Selection Tool, the second tool down on the righthand side tool bar.
Now, we will be highlighting the interior faces and holding down to CTRL tool until you've selected all of the interior wall like this.
Next scroll your camera outside and face the wall you're about to delete, it should look like a spider web like this. And keep holding down CTRL.
Now, we press the delete button and all the interior hidden faces will be deleted.
The inside will look like this.
And the outside faces will still look like this after you delete the interior hidden faces on the object.
Now simply repeat this process and you'll have a object made in Google Sketchup and transferred over that is now much much lower in poly level.
If you need any help with this process feel free to PM me.