This paper examines the bus rapid transit (BRT) legacies of mega sporting events (MSEs) held in the Global South cities of Cape Town and Rio de Janeiro. It discusses the extent to which these transport systems have been operationally sustainable, post-MSE; in other words, their ability to be maintained at a certain rate or level and hence their ability to act as public good as planned and according to specific needs. It argues that in both cities, long-term operational challenges have emerged due to conflictual temporalities between the priorities of the MSE and the mid/long term requirements of a transport system, supplemented by a poor spatial contextualisation of BRT design. These include financial viability, providing a service with appropriate frequency and capacity, integration with other transport systems, and resilience to external shocks such as extreme weather. These findings have key academic and policy implications both by opening further areas of research towards MSEs as a tool to deliver sustainable urban transport, and provides important lessons for future MSE hosts and cities considering BRT.