Implementing bus rapid transit (BRT) in systems characterized by a strong presence of weakly regulated private bus operators can be categorized along a “force-foster” continuum, representing the range in effort to replace incumbents. We examine the fostering end of the spectrum in terms of the consequences of incorporating, rather than replacing, existing operators. While the immediate effect enhances the political feasibility of implementation, what are the longer-term consequences on project sustainability? We hypothesize that the short-term political gain from involving existing bus operators may a) negatively affect performance, b) reduce leverage to regulate the emerging system, c) increase operating costs, and/or d) constrain the ability to expand or integrate the system in the future. We test our hypothesis by examining four BRT corridors implemented in Mexico City between 2005 and 2012. Our findings confirm BRT’s potential to transition away from weakly regulated, privatized and atomized systems and empower the state as planner and regulator. We also find longer-term challenges, particularly in the form of non-explicit subsidies to the system and related expectations for subsequent negotiations. The cases suggest that, when managed without a healthy dose of conflict, compromises can be costly. Cities pursuing a “fostering” approach to public transport industry transition should take note.