Different conductor rail on DLR certainly helps because the train picks up from underneath the rail so the contact doesn't get iced over. Overhead power is also better - at least until the power wires get so loaded with ice they collapse under the weight. That's probably not a problem if the line is in use because the power wire will stay warm. Unfortunately, it would be rather expensive to convert the whole third rail network to a different type of conductor now so heating it, sweeping it and applying de-icing fluids are probably the most practical solutions.

Interesting to see that Southern have also given some attention to the problems of staff actually getting into their depots too - although I guess that if the roads are closed there will still be problems with staff getting to work...