Earlier quoted context omitted.
On the other hand.... "Unification to standard gauge on May 31 – June 1, 1886 [United States] In 1886, the southern railroads agreed to coordinate changing gauge on all their tracks. After considerable debate and planning, most of the southern rail network was converted from 5 ft (1,524 mm) gauge to 4 ft 9 in (1,448 mm) gauge, then the standard of the Pennsylvania Railroad, over two days beginning on Monday, May 31,…
Amazing. I wonder if one can do anything like this with the current concrete sleepers and thermite welded tracks.
The sleepers are molded with preset widths, however, and would need replacement.