Over the past two decades, Canada has delivered, and continues to deliver, a significant programme of major light rail and metro systems, including Canada Line, Confederation Line, Eglinton Crosstown, REM Montréal, Trillium Line Extension and Calgary Green Line. While many programmes have been highly successful, others have experienced significant challenges during integration and entry into service, reinforcing the importance of robust Systems Engineering, Safety and Assurance (SESA) arrangements throughout the project lifecycle. One of the most important lessons learned is that successful integration and assurance is not just about standards, processes and documentation. It is also about people. Time and again, projects have shown that the success of systems engineering depends on the ability to align project teams, designers, suppliers, operators, maintainers and regulators behind a common objective. In many cases, winning hearts and minds has proved just as important as managing requirements, interfaces, hazards and verification activities. Drawing on lessons learned from Canadian rail projects, this presentation explores how a practical and proportionate SESA approach evolved in response to both successful and challenging project outcomes. Aligned with CENELEC EN 50126/8/9 and ISO 15288, the approach demonstrates how effective systems engineering can improve integration, reduce delivery risk and support the successful introduction of complex railway systems into passenger service.