This is a strategic move: it makes it easier to move weapons within Europe and makes it much harder for Russia should they invade.
Ideally you would want to do this all over Europe.
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Ideally you would want to do this all over Europe.
It sure is standardized; the problem is that there are so many standards to choose from!
See https://en.wikipedia.org/wiki/Loading_gauge for an overview.
Britain is a bit special, in that as the first country to have extensive rail infrastructure, it also has the smallest loading gauges around. Later built railway networks tend to have bigger loading gauges.