"In 2023, it became the first metro system in the world to operate entirely on electric power."

That is very confusing. Most of the article seems to be about metro systems (a.k.a. underground, subway, the tubes, etc.). What happened in Oslo in 2023 is they electrified their bus lines (i.e. surface transport). I think most actual metro (sub surface) system have been entirely electric for quite a while.

weird that the Milan metro system is not there