This said, what I would be worried about with this system is how long it will take for the employment market to adapt to this/those schools. When it comes to jobs, French companies, especially large ones, have a really strong bias towards applicants from well known and somewhat elitist public schools, no matter how efficient those might actually be at their jobs.
Unlike the US, France doesn't really have a strong and major software industry competing for raw programming talent, so developers have nowhere near the salary, status, or lifestyle they could expect in places like SV or NY. Very few companies have a real incentive to hire a great programmer over a good one, which might reduce the efficiency of a school that focuses on training very good developers without giving them the access to the prestige of the (also free) traditional public schools.
It will be interesting to see how salaries and career paths available to programmers trained at École 42 will compare with those hired after they graduate from École Centrale Paris.
Nevertheless, I look forward to hire from this talent pool.