Though you have to wonder how the metro systems in places like
canada and oslo manage to run when its -20C and snow a metre deep.

Because they get those conditions every winter and are completely
geared up to dealing with them?

No, actually, we don't. When Toronto had a storm in 1999 that did
produce about 1 m of snow over two days, the above-ground parts of
the subway system had numerous problems. It has top-contact third
rail with a coverboard. Normally the trains brush the snow off the
rail before enough can settle to cause a problem, and all they have
to do in case of a snowstorm is to run some trains overnight on the
above-ground sections; but with the big snowfall there was nowhere
for the snow to be brushed *to*.

The same storm caused similar results in Chicago, which is at about
the same latitude but has uncovered third rail and their system is
mostly elevated.

In Montreal, on the other hand, snow is not an issue because the Metro
is entirely below ground.
--
Mark Brader, Toronto | "This man must be very ignorant, for he answers
| every question he is asked." -- Voltaire

My text in this article is in the public domain.