Nationalization is bringing something under public ownership.
What Spain does is bringing them under public authority, but not under public ownership.
The term “nationalization” is not correct here IMHO.
How does nationalising work in the real world in a scenario like this? What happens to the private facility owners?
It's temporary. The United States and tons of countries have done it before. Central planning helps allocate resources more efficiently in times of crisis.
that is the first smart non-obvious move I've seen someone do. (off the top of my head, there might have been other ones that skipped my mind)