

It doesn’t matter much, changing bogies is a relatively quick and easy task, they could use that money better for other defense development.
The Russian military recognized as early as 1841 that operations to disrupt railway track did not depend on the gauge, and should instead focus on destroying bridges and tunnels
https://en.wikipedia.org/wiki/5_ft_and_1520_mm_gauge_railways
Tanks and jets also pose some amount of obstacle, and they may have a better roi.
Until the Helsinki Talllin tunnel is built it doesn’t make a lot of sense.