Self charging hybrid is easy, they should be considered ICE no doubt IMO.
But I agree it’s more difficult with plug in hybrid. Because they may drive 90% as an EV, or they may drive 90% as an ICE car, that was just cheaper because it had a tax advantage.
Problem is if you tax them close to EV, it will be exploited by people who kind of use them just like ICE cars.
However in Norway it will soon not matter much, because all cars that have any kind of Internal combustion engine, is considered ICE, and will be illegal to sell from 2025!
Maybe a bit dramatic, but if they are already at 80% EV of new car sales, they are definitely on track.