If we base our numbers off the Mercedes truck elsewhere in the thread [1], then that takes 1 hour to charge a 600 kW battery, which can go for about 600 mkles. If we assume a speed of about 60 miles per hour, then that only requires a bit over 10% of the road to be electrified (60 miles out of every 600, I'd recommend splitting it up to 15 miles every 150). And maybe add a bit more to be safe, plus charging at rest stops in case the vehicle is low on battery when it gets get on the highway, and some more depending on the terrain (e.g. more up mountains than down).

That being said, the Volvo being discussed only charges at 180 kW/h, and the article doesn't have battery or range information.

[1] https://news.ycombinator.com/item?id=38315909