The governance of urban mobility is structured around interdependencies between actors through complex socio-technical systems. Whether they are public or private, formal or on the bangs of a state organization, urban transport services are confronted with territorial cohabitation and thus create relationships of mutual dependence. In the light of the sector’s modernization projects, the integration and unification of transport systems is a key public policy objective. Interdependencies between actors (operators and regulators) are at the heart of the digitization process. The “Integrated Mobility” project implemented by the organization in charge of mobility in Mexico City (secretaria de movilidad or SEMOVI) in 2019, represents a privileged observatory to study interdependencies within a particularly fragmented set of actors. This work is based on field surveys conducted in early 2021. The article identifies interdependencies between actors as a fundamental key to understanding transport system integration projects and policies. It highlights the limits of social and political organization in the face of technical challenges and the promise of digital technology. Finally, it questions the implementation of smart mobility and its articulation with the concept of Mobility as a Service (MaaS) in a context of fragmented urban mobility.