If the externalities they're pricing in are oil consumption in the vehicle, and the vehicle doesn't burn oil, setting the taxes to zero is "proper pricing".
That's not the only externality; another one is wear-and-tear on roads. In most countries, fuel taxes are used in part to pay for road and highway maintenance [1]. Certainly Norway's extensive, mountainous highway system is not free to build and maintain, and imo all road users should pay their share to fund it. You could have a direct per-km tax enforced via some kind of GPS unit, but that has privacy implications. Traditionally the fuel tax was a reasonable proxy, since vehicles used fuel in rough proportion to the amount of road traversed.
The vast majority of road wear and tear is caused by trucks, not cars:
"Heavy trucks obviously cause more road damage than cars, but how much more? According to a GAO study, Excessive Truck Weight: An Expensive Burden We Can No Longer Afford, road damage from one 18-wheeler is equivalent to 9600 cars (p.23 of study, p.36 of PDF)."
With regards to your point to taxes, remove the per-milage tax and charge a flat per-vehicle rate based on vehicle class, distributing the cost to trucks more than to passenger vehicles.
