When selecting the top and tail formation with the MK2 coaches in the scenario planner, the game will crash upon loading the scenario. This appears to happen on every route so it must be an issue with the formation itself. Im not a betting man but I would wager it's because the MK2 coaches are tied with NTP and that route hasn't been brought forward to TSW 2 yet so the game is trying to load an asset that doesn't exist.