Yes, judging from the size of the wagons, it is most likely on one of the main lines, which were (and still are) 5ft/1524mm Russian gauge.
For 28mm, it depends on what your chosen model scale will be, and what visual effect the rail gauge should have. So, if you went for 1/56th scale for the cars, the nominal track width for 1524 would be around 27mm. There is, however, no such gauge, and unless you want to re-gauge existing rails (for example taken from HO/OO Flexitrack, as I did for some table modules once), your best bid would be 0 gauge tracks, which have 32mm track width. Obviously, this is a bit too wide, but on the other hand, it will make your cars more stable, especially if you place figures inside, and it actually looks more "wide-gaugey" than an accurate track would look.