This paper analyzes the construction of a public transport policy on an agglomeration scale through the case study of Lyon, France. Its metropolitan government structure evaded the problem of serving large social housing areas. The founding sequence of Lyon’s intercommunality sheds light on the politicization of « communautés urbaines » observed during their first decade of existence in France. The specific city of Vaulx-en-Velin was granted several thousand social housing units. The municipal councillors meant to use them in order to provide modern urban equipment. But, within the new intermunicipal arena, the exacerbation of hierarchies among elected officials undermined the resources of municipal communism. The trajectory and the resources available to Vaulx-en-Velin’s elected officials predisposed them to use conflictualized reading grids of the social world, in order to endorse a role as representative of the town’s working classes. The intermunicipal politicization’s de-singularized the service of neighbourhoods, in order to transform it as a local public problem that calls into question the global treatment of urban working classes.