Electric cars make sense (at least in Ontario)

I had a long-standing question about electric cars answered for me the other day, by (who else?) the good old Globe and Mail.
Electric cars always seem like a good idea - or at least they will be when the battery technology and the costs improve a bit - but I always had this nagging doubt about how much greenhouse gases (GHG) they really save, given that they use electricity from the grid as their fuel, which carries with it its own GHG load. I've never seen this issue addressed.
A paper published recently in the journal Nature Climate Change answers just this question. It turns out that shifting to electric vehicles will only reduce overall emissions if the plants that make the power used to charge the cars generate less than 600 tons of greenhouse gases for every gigawatt-hour of electricity they produce. So, given the relatively good GHG profile of my home province of Ontario's electricity production, electric cars make sense here (and in other responsible provinces like Quebec and British Columbia).
In fact, Canada as a whole produces power at a level of about 200 tons of GHG per kWh, well below the critical level. But, as we know, not all provinces are created equal, and places that still have lots of coal power plants (calling out Alberta and Saskatchewan) spew out about 750 tons of GHG/kWh produced. So, switching to electric cars there would actually worsen the overall GHG situation.
Worldwide, the rate of GHG from electricity production is apparently 536 tons/kWh, and so marginally below the 600 ton threshold rate, but this of course hides some large discrepancies between countries (and within those countries). Therefore, electrification does not actually make environmental sense in counties like India, China, Australia, Saudi Arabia and Indonesia, whose GHG production from electricity generation is bad.
So, there you go: wait long enough and the good old Globe will answer your questions.