Re: Maybe 1 in 1000
40% of all cars registered in Norway in 2017 were electric or hybrid.
In Europe as a whole, plug-in electric cars were 1.4% of new registrations, which means we are probably not far off your "1 in 1000" of cars on the road already. (It will vary how you count it - electric vehicles probably do shorter journeys, so a lot fewer than 1‰ miles will be by electric vehicles).
Norway plans to ban new petrol/diesel cars by 2025 (which is 8 years away, not 30).
Even France and the UK plan to ban new cars by 2040 (which is rather less than your "30 years", but is distant enough that it could easily slip).
I think one in three by 2028 is quite plausible.