[Suicide Junkie]

After making desision to use one, changing to other would require massive scrappin of old and replasing all those former bolts and screws that have now become "absolite".

You mean "obsolete", I'm sure.
That's a fair start, but the imperial to metric conVersion will only take a generation or three if you try.
Probably the closest Space Empires analog to the railway idea would be Standard extractors to monoliths... you have to scrap the old and build the new from scratch... at worst, an entire planet at a time.
You'd have to lay down new track across your country/province/state, then get new trains, and tear up the old tracks, redesign the stations perhaps, but if the economic incentive was there, or if I became dictator for life of the country, it could happen .

Major changes would be rough going at first, but if you want it, you could still do it.

---Extended response stuff moved to new thread---