Let's make things clear: so called "mixed society" is actually a mix of "friends of the Mayor and allies" and poor-enough people that will vote for the so-called socialist Mayor. It's not about having a philosophical or idealogical view of society, only a practical view of election (a kind of "gerrymanding" if this concept is more understandable for US).
There has been frequent scandals with ministers still using "low income" housing for themselves or families. The article starts with the interview of some Ms Vallery-Radot, and that uncommon name prompted me to look on internet and wonder if she is related to the https://fr.wikipedia.org/wiki/Vallery-Radot which was until the 2000 ... State Advisor.
So please... do not think that Paris is some kind of wonderful place where intelligent and humanistic leaders are working for the good of the french society as an example to the world. It's just usual political shady business, nepotism (and you'll see by yourself that the results will be bad during the Olympics for example)