Been reading and thinking a bit more. This area could suit the way EPH's old Orient Express scenario was done: have the option to start in different countries, with different benefits and drawbacks. As far as I understand it so far, in the inter-war period it went like this:
1/ Russia hated everybody.
2/ Everybody hated Russia.
3/ Estonia and Latvia were on good terms.
4/ Latvia and Lithuania mostly got on, but had some disagreements over exactly where the new border should go (resolved peacefully, if slightly grumpily).
5/ Lithuania hated Poland.
6/ Poland hated Lithuania.
7/ Latvia doesn't seem to have been too bothered about Poland.
8/ Latvia and Estonia didn't like Germany much at all (although they would still trade with it).
9/ Funnily enough, Lithuania mostly got on with Germany (Germany had helped them against Poland).
That's the political basics in the period, and goes some way towards explaining how the various countries behaved when the next war arrived. Moving right along...
Estonia had stacks of cheap oil, meaning very low fuel costs for rail. That's all they burned. Latvia had no oil or coal, so was initially dependent of wood for locomotive fuel, then started moving to imported UK coal in the 1930's. This seems odd. Estonia was happy to export oil, and the two countries got on well, and importing coal from the UK presumably wasn't cheap. Maybe Latvia had no exports that Estonia wanted. The UK and Germany seem to have been the two big export markets for the three Baltic states. I suppose ships going between Latvia and the UK would naturally be looking for a return cargo, and at the time the UK was a huge producer of high grade coal so...
Exports were mainly agricultural products at first, and stayed that way in Lithuania. it was the least developed of the three, although there was a shift in what sort of products it specialised in (dairy and meat were better value as exports). Estonia had its oil industry once production got moving again, was also big on exporting dairy products and timber products, and oddly enough it was also a pretty big manufacturer of textiles (had been one of the largest in the world in the late 19th century). It has also been in the paper business in a big way for literally centuries.
Latvia's main exports were agricultural and timber products, but it also ended up with a good electronics industry and some other manufacturing (like world famous miniature cameras, etc) and even got into producing automobiles in the mid to late 1930's. So all things considered there's some good scope for economic variety.
There's also good scope for variety in locomotives. The short version is all three countries got locos from the big countries that had been on the losing side in WW1. Estonia ended up with Russian rolling stock. Lithuania had German rolling stock. Latvia got all sorts of odds and sods. Estonia and Latvia also had about as much narrow gauge as main lines, if that can be finangled into the scheme somehow.
Oh and the 1.06 Russian Class S 2-6-2 wasn't actually used in Estonia.* I suspect this is because at the time it was Russia's latest and greatest express choof, so they preferred to pay their war reparations with older stock they had plenty of, mostly the O class 0-8-0 and the N class 2-6-0. Speaking of 2-6-0-'s, for some reason they were the most numerous type in Latvia but I don't know which classes they were (information is hard to come by). Probably one of the Prussian/KPEV classes though, since they seemed to end up all over Europe. The P6 and G5 would be likely candidates.
I do know Lithuania got some P8's, but at the moment I don't know what else they had.
*Edit: I just realised that the "
photo of a Russian gauge 2-6-2" on Latvian track shows one of the Class S. Funny that Latvia would get one when Estonia didn't, although it could be a Russian unit near the border. Latvia did maintain some Russian gauge tracks.
The preceding photo on the same page, showing a 0-10-0 being offloaded at Riga, is one of the Russian E class that was contracted to be built in either Germany or Sweden just after WW1 (
details here: use
Google or
DeepL). It wouldn't have been used in Latvia. It just would have used Latvian track to get from Riga to Russia.