I'm afraid so.
What you can
do with GE kml files in conjunction with RW_Tools is to turn them into series and named routemarkers.
I'll explain by telling you what I did with my route.
Using GE I carefully (you don't want to do this a second time, trust me) drew a line over the (mainline) track and saved it as a kml file. When you pull this through RW_Tools, you can turn that into a line in RW over which you can now overlay track. This is a series routemarker.
Using GE I carefully (you don't want to do this a second time, trust me again) placed a marker over each quarter-milepost on my route. Again process this with RW_Tools and in RailWorks edit mode you will get a flag where each milepost should be in RW. I did a similar thing with gradient markers which meant that I could get pretty accurate track grades. I also did it with bridges, crossings and all relevant points of interest. These are named routemarkers. In edit mode, if you press F6, you can display the text you assigned which is great for gradients but since the text always faces you, be careful setting you track grades. Have your paper route documentation with you and put check boxes against each item. Tick them off as you do them. Track gradient changes have no undo so be careful
. Add a gradient adjuster post for each gradient change on the track. Save profusely. And backup regularly. Go round after with the terrain magnet and suck the terrain to the track.
It's a bit like decorating a room, everything is in the preparation. If you now have all this geospecific information, you should be able to concentrate on creating your route without being concerned about where things should go. It's a painstaking process but should give you a good foundation on which to build a world class route.
I'm sorry to say that there are more pitfalls but I didn't want to turn this into 'War and Peace'. You will discover them as you try this out. Maybe just start with a couple of miles of track.
I did one further thing and used RW Decal for each of my station and siding areas for use with setting track and buiding positions.
I only have one thing left to do with my route and that is acquire some talent for adding scenery to 23 miles of route. Hmmm... I'm going to have trouble with that.