Well, it looks like *you* have never been to Paris. Most people working in Paris live outside Paris. And there, you can easily find a route not covered by train/buses...
When how is that a problem?
They can do like lot of people do: They can use their car to reach the nearest train station and from there, use trains/RER/subways/buses etc. TFA doesn't state that SUV will be banned outside of Paris too.
On a side note, I live near Paris, I work in Paris. I don't have a car, and that's fine.
I'm not saying that car is bad. When you have to move furniture, or stuff, or in some other situations, car might actually be the wise choice.
But, from my experience, that's not how it's used. There are like 9 out of 10 cars used for only driving 1 person. And that's sad. I'm breathing this air.
So when it comes to diminution pollution, i'm all for it.