Kraków's Magic Carpet Ride on the Last Train to Clarksville

[swaghauler]

No, just the same gauge.
A quick search online shows that most countries use Standard Gauge of 1,435mm.
Finding information on the rolling stock used by the PKP (Polish State Railway) is...difficult. This could well be because there's many, many different types in use and no particular "standard" size.
I did find though that flat cars throughout the world (mainly US sources of info though) are approximately 12-16 metres bumper to bumper (so a little less actual cargo space), some shorter, a (very) few longer.

There are two standard length railroad flatcars in the US during the Twilight War. The 55ft and the 58ft both with a 10' 4" width and the standard 25ft height limit for tunnels and bridges. These flatcars both hold 159,000lbs (roughly 72 tons) and are much more common than the previously mentioned 89ft heavy rail car. Many of the people in this forum have probably seen them rolling along with TWO 53ft (102" wide) Semi-trailers stacked one on top of the other. As much as we haul in trucking, the standard "big rig" doesn't hold a candle to even ONE railroad car. Outside of commercial shipping (river barges and freighters), NOTHING moves freight like a train can.

Looking at the MI-8, it is 60ft long, 18ft high, 10ft wide, and 27,000lbs with a full load on board. Nothing here would be an issue for even a standard railroad flatcar and an 89ft "heavy" (which can carry TWO M1 MBTs) would still have more than 25ft to work with.