Before we get too excited about styrene rail-
As one member said- what about the rail we already have? One reply was weight but that is not an issue unless you are going to "haul it." And most of the suggested uses by members didn't seem to lean that way.
But I'll suggest the real issue is going to be manufacturing the stuff with the right profile and at a good cost. It's not like the sheet goods nor the strips and tubes. I'll guess that to extrude the profile of a rail will be more of an issue- especially consistently and in some of the suggested sizes.
Who knows I might be wrong but those of us scratch building is a minority of model railroading and those wanting styrene rail probably even more of a minority. Be prepared for a "polite no."
Now that being said- maybe someone on the list will suggest a way they make small quantities for their projects. Even with a CNC that's not the first thing on my list of projects.