One issue that I have with mandating electric cars is that they may not be "the" solution to the carbon problem. Hydrogen, either burned or in fuel cells, could be a highly viable option. If somebody comes up with a way to produce it relatively easily in high volume, particularly locally so it doesn't have to be transported long distances, H2 infrastructure could be built up much more readily than electric because it won't require massive power generation and grid upgrades.
My concern is that those ridiculously expensive power/grid upgrades will happen spurred on by pressure from the auto manufacturers and "green" lobbies, then become unnecessary... leaving us taxpayers to foot the bill since it's likely to be highly subsidized. It's like buying a VCR in the '80's... BetaMax or VHS? And the ultimate answer was... streaming over the Internet.