I am talking about resetting cameras for at least the exterior and interior views of the train in the game, got it?
There are no hard settings to those, restarting the game - or even scenario - will reset them. During the scenario, you can change those views in two ways: The cab camera (1) can be cycled between various seat positions. Left-right buttons allow you to rotate between them. Car follow views (2-3) cannot be entirely reset. Up-down button changes the distance, the rest is mouse and ... Free view (8) preserves zoom level, set with the mouse wheel. You can also move around with the direction keys. Direction keys have modifiers with Shift and Ctrl, what they do depend on a few things. Try them out. In contrast to this, the Shift+F2 lean out view doesn't preserve zoom. External cameras cannot be used in tunnels, only 1 and Shift+2.
