1. I did some rough calculations with some number pulled off Wikipedia, and basically, if everyone went to electric vehicles, we'd have to double the elecrticity supply. On the other hand, our recent experience with rewiring everything for the internet suggest that large scale upgrades to the infrastructure are doable, just so long as we give them some time. If we gradually introduce electrics, and don't insist we swap everything over by next Tuesday, we should be able to handle it.
2. I'm just south of you in Calgary, and I've had the argument with people how bicycles and public transit just aren't going to cut it for everyone. Of course, the population isn't evenly distributed, and there are clumps of population where electrics might suit people's needs just fine, just as long as people don't fall into the trap of thinking what works for them, works for everyone. Maybe plug in hybrids are the short term solution. Use the electric drive for around town, and switch to gas for long trips.
3. On paper at least electric power's ability to deliver full power even at low speeds would be ideal for trucks, and seeing how those monster haulers in the oil sands use electric drive, you would think it would be possible to make an electric motor with enough grunt to satisfy even the most demanding trucker. Like with 2, range is a big issue, though I can see the cost of electricity vs. diesel making electrics attractive for short range commercial vehicles, depending, of course on how much it costs to switch. It'll be interesting to see how Tesla's pickup and big rig fare in the real world.
4. That's a good question right there. Batteries do not like the cold.