As an example for Paris, the oldest subway line (https://en.wikipedia.org/wiki/Paris_M%C3%A9tro_Line_1) is fully automated.

There are some of the cars on other lines (like line 10 I'm taking to go to work) are more than 40 years old (https://en.wikipedia.org/wiki/MF_67), but they've been through some refurbishment since then.