I believe that the Soviet Union rail gauge was common with both the United States and the United Kingdom.
So a special rail gauge for countries starting with a "U" then? I wonder if Uruguay was part of the club?
Also consider that it wouldn't make sense for the USA or UK to send lend lease locomotives to the USSR if those locomotives wouldn't fit on the existing tracks.
While they couldn't send existing stock, they could build new ones with the Soviet gauge in mind (or the Soviets may be able to modify once they'd received). If the game was to try and start tackling equipment compatibility issues though, I'd argue it should start at the division level - at the moment there's no cost for having a division using oodles of different types of equipment, when it was generally more efficient for supply to have standardised kit.
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