The RATP, which is the Metro Company in Paris, has installed several defibrillators in the metro. In theory, as explained clearly in their website, the device is designed to be used by people who have never used one before. It is a public-spirited gesture that needs no prior training.
Now, let's imagine the scenario: someone is laying unconscious on the floor next to this sign. The rescuer, in all probability not a medical doctor but a common person obviously in the middle of a panic attack, picks up the inter phone looking for help. The voice on the other end of the phone most likely will say: "RATP a votre service, le poste de votre correspondant est occupe, nous vous demandons de rester en ligne et vous remercions pour votre comprehension". Let's face it: how many times do you hear French talk in English? Not so much. Additionally, this is one of the most touristic place on Earth. The likelihood that a non-French speaking (average tourist) vs French-speaking (resident) rescuer will use this device is really high.
That being said, kudos to who had this idea and good luck for the unlucky guy who will need it.