With the central importance of railroads to the story, you can't really set it anywhere near our present. Between Amtrak and the castrated freights in this country and the hollowing out of American steel and automotive, the book becomes preposterous.
Trying to modernize the whole industrial universe (Taggart Rocketlines, Rearden Carbon Composites, Wyatt Biodiesel) would be ludicrous.
Personally, I envision it set in an alternate-universe 1950s, when America still dominated these industries. Lots of tailfins, Art Deco and those streamlined visions of a Jetsons future.
Jolie was in Sky Captain and the World of Tomorrow which conjured up a futuristic 1939. There's a lot in that film's style and decor that might be adapted to a similar project, though outright copying wouldn't go. It wasn't a very good story, but the look was fascinating, at least at the beginning.