I wasn't sure if "Fright?" was meant to ask if there was a freight rail line with a connection or if you were suggesting that freight traffic would provide the demand.. If the former, the Alaska railroad does not have a rail connection to other railroads in North America. It looks like barges are used to link it to the North American rail network.

https://en.wikipedia.org/wiki/Alaska_Railroad

Basically, I'm guessing that people in this thread assumed "rail = passengers" but I'm guessing that's not why a rail link was proposed, that's all. Passenger rail barely makes money (in the US) running tiny distances between population centers. It's probably not going to make money going from the middle of nowhere Alaska across an ocean. But clearly the idea came from somewhere.

The great circle air route between Chinese manufacturing hubs and SFO passes quite close to Anchorage. Not sure why they stop there--refueling isn't necessarily needed so it's probably a hub to offload some cargo for points further east. Going up through Russia and under the Bering Strait would actually go quite a ways north of that route all other considerations aside.

Cargo doesn't care about the inconvenience of stopping for gas, and that allows cargo airlines to load the planes heavier (remember that much of a passenger aircraft is filled with air, not cargo). Anchorage is also within a 9-10 hour flight of almost the entire developed world, and massively overbuilt from the days when trans-Pacific aircraft had to stop there due to range limitations.

Yup - Anchorage International is the 2nd busiest cargo hub in the US (after Memphis).

Refueling isn't necessary (there are daily nonstop flights from Washington, DC to Beijing, for example) but having an intermediate stop may allow them to carry more cargo on each flight, as air freight is probably weight constrained rather than volume constrained, and less fuel would mean more weight left for cargo. (I could be wrong on that, of course!)

Looks like you're right: http://www.adn.com/article/20130630/fedex-cut-trans-pacific-...

It also looks as if the FedEx was using planes that didn't necessarily have as much range as typical passenger aircraft today.

But is there actually enough demand to justify the middle ground?

Seems like the US imports quite a bit of stuff from Asia.

Right, but it also seems massively expensive build rail from Russia to Alaska and from Alaska to the rest of North America. I'm not convinced there's enough demand for imports on the particular schedule of rail to justify that massive expense.