I think you are right, here they limited the tax free registration of EVs to 2011, in 20012, they will cost registration fee.
The same will happen to petrol - as less petrol the cars use, as higher will the tzx be. At the moment, one liter costs about 2 dollars, and the most of the price is taxes.
In Denmark, every car pays every half year a tax, depending on the consumption, the Smart is the second lowest possible tax, only the VW Lupo and Audi A2 are cheaper.
In addition to that you pay a tax on the car insuranse.
of course you pay the usual VAT (25%) on spare parts, cars, and everything you by to the car, you pay parking fees to the state, you pay 180% registration tax, numberplate tax and so on. A big part of the danish states money comes from car taxes, so it would not be possible to drop it.