Go look at the map of the L'Enfant Plan. Now compare it to a map of modern-day DC. They aren't the same: the modern city is much larger. The original plan just covers the federal district, street layouts, etc. Georgetown is just a name on the side of the plan, for instance, with no actual plan. The original plan certainly doesn't include the subway system, or Union station and all the train lines, or many many other things.