I’ve not played CIM, CIM2 or CSL. Did left-sided driving get implemented in CSL?
Apart from text-reversal, another potential problem is that back-faced culling might be affected. To solve this, either the direction of the vertices in the polygons needs to be reversed, the test for the Z-component of the polygon-normals needs to be reversed, or the X-component in screen-space needs to be reversed after the back-facing polygons have been culled.
As for text being the wrong way round, I’m not sure how easy it would be to automatically reverse texture-co-ordinates on models (is doing this automatically even feasible). The only idea I had is that LHS-country-themed vehicles and buildings would have mirrored text and RHS-country-themed vehicles and buildings would have unmirrored text. Of course this would create problems for anyone wanting to mix text-containing vehicles and buildings from LHS-countries and RHS-countries, although one advantage mirroring does have is that the doors on busses would be on the correct side regardless of where the bus was from.
I’ve not tried this myself, but I think you can get trains to drive LHS by placing the signals between the two tracks instead of on the edge (it works but signals in the middle instead of the sides does not look so nice). Also, making the trains run LHS using this method might confuse the pathfinder (although I’m not sure about that).