One one hand, I think China developed an engineering solution to laying track across tundra and permafrost on its line to Tibet, and the Alaska Railroad also runs all year on tundra. On the other hand, BC Rail did a lot of work grading its Dease Lake extension in the 1970s, and it seems like a more practical idea to revive the Dease Lake extension, which I believe was always meant to eventually reach Alaska as well.