Could anyone get a gold medal for this mission? It took me years to get a silver, but gold seems almost impossible...

It was the one scenario of the Campaign I never got gold on.

Tried a couple of approaches such as demolishing lots of track to reduce maintenance, leaving the track and just running loads of trains, leaving track and running a few high value inter-city etc

never succeeded.

Did it last night on hard and grabbed the gold about five years ahead of the deadline.

Go with the passenger revenue bonus and focus on long-haul passenger+mail routes with diesel trains, plus revenue-boosting buildings at the stations. Favourable business cycles help too...

Agree with Murphi. Did it years ago (base game, retail CD). Wrote myself mini walkthrough notes, which start:

"One has to achieve a high company book value in a short time. To do so one must aggressively go for high profits early on (to become creditworthy enough to issue lots of bonds, since one cannot go to the stock market – an early economic boom will be a great help here). I went for long-distance passenger routes, with hotels and restaurants at the stations, but a limited train service taking only a fraction of the available passengers and mail (to keep the demand and hence fares high).

"I bought a couple of Prairies first, then cheap Hudsons until the game stopped making them, after which GP9 diesels became available. (For my first few years I had the Hudsons hauling 4-car trains for extra revenue, until I discovered – the hard way - that I was running them into the ground) Whilst running a steam-and-diesel north-south main line, I then started an electrified east-west network."

Not all existing track or stations are helpful. Ignore what isn't. "Any old track not being used still contributes to company book value, so if it isn’t in the way then leave it lying there."