Wasn't there talk in our post war era about keeping some steam in storage for national emergencies.

I believe Poland held onto stored USATC S160s well into the '90s in the event of a Soviet Union invasion. They ended up destroying them with leftover Cold War munitions that they had lying around and also needed to dispose of, rather than waste money on acetylene.

Not quite. I think you have your "facts" a little scrambled. Poland was a member of the Warsaw Pact and as such an ally of the Soviet Union, although maybe a somewhat unwilling member, so they hardly had to fear an attack from them. And where did you get the idea that they blew up their obsolete steam engines with ammunition they had "laying around"? Hardly an efficient way of disposal of either.
Sounds like a glorified wives tale.

Regauging SOME key lines by adding a third rail might be a faster and temporary move. It would still require more complex switches but there was a lot of three-rail trackage scattered around this country. Detrucking and retrucking from the European common (Standard gauge?) to broad gauge would be labor intensive and slow. If we are talking about grain trains, it might be easier to build a few large transloading silos. I would build them outside the borders of Ukania and extend the broad gauge to them. A few less Ukranian targets.