I've figured the scenario out in the meantime via extensive trial and error, beat it few times, even attained a gold medal eventually and... wow. One of the better maps I've ever played or recall seeing. The sheer nostalgia factor for me (I'm a huge fan of "The Postman" by David Brin and this scenario fits right in) made it a great experience and then there is the whole logistical puzzle to figure out. I absolutely love how everything in the scenario connects together, rathen than having some obscure resources. Well, aside maybe canned coffee, but compared with other maps, this is a golden standard of connection between resources and goods.
However, there are still issues that I was unable to figure out for high efficiency, instead simply removing non-essential trains once I've got all the rails I need laid down, because even with three lines going, it's a mess. And a LOT depends on early RNG, since not having Chemicals in Salem/Eugene/preferably both or having Coal scattered around can make things absurdly complicated. I also end up restarting few times when I realised there are no Dairy Processor around, or having a single Milk producer in the Valley.
Anyway, stuff I still have and can't figure out
Any dam that isn't Detroit one (the north-most) is a complete pain in the ass to connect with rest of the rail and a sink for rail cells, while you might end up with any of those dams getting destroyed right after being connected. Not a single line created by connecting any of those southern dams has any practical applications, unless I'm missing something. At least Detroit Dam is on the shortest and most effective route to Madras, but other three are painfully hard to connect
Connecting to the Grant's Pass military depot has absolutely no way of avoiding high grades, unless openly cheating (by stocking up high amount of spare rails and then lowering the terrain by building at angles, demolish the rail and build new line in the now "flat" terrain. The fact you need to haul Oil from Salem to... Roseburg and then to Grant's Pass only works in three stages, otherwise the line(s) between Eugene/Veneta to Roseburg gets blocked in no time, even if nothing else goes there.
If for whatever reason Chemicals don't spawn in Salem/Eugene, the scenario is close to impossible to win.
If there is no Workshop turning Steel into Goods, things get wonky ealy on, since connecting to... Siletz? The place with Ammo factory. Anyway, Steel deliveries provide a lot of rail cells, so without a quick dump of entire Steel production from Corvallis, there is lotta steel that does nothing and railway to ammo factory might take even 3 years to finish.
I was absolutely unable to get Alluminium production going in effective way. I know you can suffice on Steel, but this undermines the whole effort to get Alluminium at all, as hauling it half over the map back and forth (and only two places can have mills) doesn't exactly work. Am I missing something, or this was intended?
Connecting to... Grand Ronde (the port you need to connect) serves nothing. The terrain makes any hauls going there impractical and wasteful, but at least it's self-contained area, so a tiny passenger train going there can pay for the tracks.
Things that I never had issues with or figured out:
Money is barely an issue, since a huge amount of resources and finished goods are going to be hauled. Passenger trains can be managed almost entirely as "side" or during "empty" return hauls. It's absolutely normal to generate 10 million of industrial profit/year if all the farms and processors in the rail system are owned by player, closely followed by coal.
Milk is the key. If Halsey, Tangent or Albany don't have Dairy Processor, just restart the map. Milk not only can carry on thanks to rail cells it grants (probably the easiest of all "farming" goods), but the food provided from it can then be quickly shipped to Salem and traded for Iron. Flooding Salem with Food is great, since it goes through customs to get Iron. Having a ready pile of Iron for pick-up speed things up significantly
Bend to Madras is a nice money maker passenger route, because it doesn't interact with rest of the rail and provides substantial income.
"Efficiency" locos are better, solely because they have higher reliability and better grade performance.
No point bothering with Lumber, while Paper is only worth to get the Mail production bonus. Same with Concrete - once the dam is fixed, no point clogging the system with Gravel and Concrete shipments. Profit is meaningless, but the slow down on the rail system is painful.
If there is no place to connect at least 2 Coal mines with single station, restart. If said Coal isn't in easily accessable spot, restart. Coal is one of few choke points of the whole system, not having it makes a difference between winning or failing.
Once electricity is back, there is no point to keep using steam engines outside mountain hauls. The sheer reliability and speed of GG1, along with compact size (so less things on the track) makes up for everything else.
I'll have to try that. Usually I connect via Detroit Dam and then next to Mt. Jefferson, over the top of the Lake Chinook's Dam. When I have spare cells, I demolish the most graded element and rebuild it, dropping the grades to a passable 4-4.5%