This paper contributes to the debate on integrating shared automated electric vehicles (SAEV) in Mobility-as-a-Service (MaaS) in Europe’s public transport system. Using the ongoing Horizon Europe ULTIMO project as a case study, we attempt to explain the process of institutional change from the old to the new dynamic institutional equilibrium when SAEVs are integrated in public transport systems. We explain that understanding the conditions, shape and form of a new institutional governance requires careful analysis, and the actors need to understand the impacts of the change. We also argue that designing generic and context-dependent formal and informal regulations in Europe's local, national, and international public transport systems requires meticulous analysis to achieve a new dynamic institutional equilibrium acceptable to all the actors. Moreover, understanding the process of institutional change could provide insight into the workable governance framework in the new dynamic institutional equilibrium.