This mod Changes - Metro and Bus System - Edition Express breaks the Transport System in XXL. I don't know if there's a work around, but once you use it, the transport system says that there are no transport companies to keep the lines. And even if you delete the buildings, save the game and remove the mod, when loading the city, the game crashes. Edit: I tested without this mod and the issue remains ! So, anybody knows any other mod that might be breaking the transport system?