If you take Paris as an example, CDG has a train station in it. The airline will sell you the train ticket together with the plane tickets so you just get a sec

If you take Paris as an example, CDG has a train station in it. The airline will sell you the train ticket together with the plane tickets so you just get a second ticket which looks like a plane ticket except for the train. You literally go to the basement of CDG and get on the train. I've done this many times in CDG and also in FRA (Frankfurt) and the tickets are issued as valid on any train between the two destinations, so even if your flight is delayed, you just wait for the next train and get on it. The train thing is really a non-issue. Your second point does however seem valid, I guess the airlines will reroute around French airports and fly to nearby countries in Europe to get around this regulation. Hopefully this law doesn't cause more harm than good...