This presentation outlines the rail industry's migration from Europe's legacy GSM-R train radio to the new 5G-based FRMCS standard, a multi-year transition planned between 2025 and 2035. It highlights the necessity of maintaining dual-mode operations during this window and details critical modernization building blocks, including Layer 2 Ethernet aggregation, Layer 2/Layer 3 switching for traffic isolation, and industrial cellular routers equipped with dual-SIM failover.