Seattle has a light rail system they only booted up a few years ago. They had to build a completely new set of rails everywhere to do it. I'll admit I don't know the details of its history, since I wasn't paying attention, but it's utterly possible.
20 years is on the long side, but I find it a reasonable amount of time to make it happen. And the point was more that it happened, and that it wasn't exactly an isolated case.
