Good question, Reg (although An Inconvenient Truth is a flawed production). From what I've read and understood (which isn't the entire report), the IMF cited two separate classes of examples of energy subsidies. First is the fuel subsidies seen in the developing world and in the Middle East, which strongly encourage increased and indiscriminate consumption of fossil fuels. The other was that lack of a carbon tax in the developed world. It think that's a more problematic conclusion, but it may well be correct.

The thing is, the mix of fuels in the transportation supply is about to change quite a bit. Discovery of unconventionals, new biofuels, and copious quantities of shale gas will have an enormous effect on the fuel mix over the the next 20 years. And that effect could last for another 100 years or more. I didn't see the IMF report taking into account a mix of cleaner burning fuels that will begin showing up in the developed world sooner rather than later.