In this game, I started by building a single surface rail line along the coast, and I chose a "sparse" strategy, building track-only (no stations) on less populated tiles. By turn 58, this line was net profitable:
Next, I moved to the south, where cities were beginning to grow on the forest's edge. By turn 65, I had a small surface rail line there (4 stations):
By turn 70, most of the population was concentrated in 11 major cities (black border in screenshot below). For the two big cities on the west coast, I chose the names Vancouver and Seattle:
At this time (turn 70), Seattle was a more desirable location than Vancouver:
That's because only Seattle was connected to my new subway system in the south:
The "Arctic Line" and "Moscow Metro Line" are highlighted below (Arctic Line in grey, Moscow Metro in red):
I planned to extend the Moscow Metro along the coast to connect with the big cities in the north, but at that time (turn 70), acquiring land in Vancouver was expensive, due to a shortage of available available land, due in turn to Vancouver's relatively high population (1.338 million):
I decided to wait a couple turns before extending the Moscow Metro northwards into Seattle. This gave people time to migrate to the more desirable location (from Vancouver to Seattle). By turn 72, drawn by Seattle's superior connectivity in the rail network, over 300,000 people had migrated from Vancouver. This made land acquisition in Vancouver much cheaper.
By turn 73, I had four cities over population one million (black border):
On turns 79-81 I used the trade winds to rapidly explore the sea in the far south and south-east.
By turn 102, I had 9 big million-plus cities:
Land value in these cities was bolstered by two metro lines. A second line was required in the north-western forest due to geometric constraints (branching is not allowed):
On turn 168, I stopped building, and just started saving money to get the 6th and final tech.
Game finished on turn 173. At this time, I had 6 cities over 2.5 million: