RPA senior planner and Paris native Juliette Michaelson provided Streetsblog with a loose translation of Baupin’s description:

It’s the neighborhood association that undertook this effort. They asked us to do it with them, and help them with logistics. They rolled out a large square of green carpet — 25 meters by 25 meters — on which they painted lane markings. They rolled it out for a short time, took a few pictures, and then returned the road to its "temporary" use – well, its temporary use for the next decade. […] The whole operation was on for about 15 minutes, it didn’t disturb very many people, but it gives you a sense of perspective. […] It’s actually an Anglo-Saxon tradition — “Reclaiming the Street,” it’s called.

I’m not sure any Anglo-Saxon has gone this far, but Baupin knows a thing or two about reclaiming the street. He’s been the driving force behind Mayor Bertrand Delanoë’s
sweeping transportation reforms, including the Vélib bikeshare system and a far-ranging campaign to convert parking space into more room for buses and bikes. All accomplished without London-style congestion pricing.

Along with this video, Baupin has posted two others about Carré Vert on his website. In the third clip, he describes his eventual plans for the Périphérique:

We are demonstrating that the Périphérique doesn’t have to be — that we can change how we think about it. We can imagine what it could become in the future, when we’ve been able to put together such a strong public transportation system that we can be less dependent on cars. At that point we could transform this awful highway into an urban boulevard with transit, cars, pedestrians and trees. So where today there is desolation, a terrible and ugly scar that cuts the city in half, we can create a city that we can all enjoy. Operation ‘Carré Vert’ is all about imagining how we can transform our city in the next 25 years.