Just thought I might get a few opinions and helpful tips on the subject...
To make a long story short, I tried converting one of my old .dst's to an asset that is workable in Railworks. By the the time I was done removing all the objects that crashed 3DCanvas, the Asset Editor, or Railworks, I only had one original part left! By the time I finished rebuilding the original textures and adding detail to bring it up to Railworks standards, the project took three times as long to complete than if I had started from scratch with Railworks in mind.
In my opine, importing and converting a .dst from TSM just isn't worth the bother.