I can't think of a simple way to "bake" in the lighting.

I imagine you're going to say more requirements that will make this suggestion pointless, such as you want to animate from different viewpoints, but here goes.

Make the side of the rail car invisible.

Render one compartment, centered in the preview. Save the render as an image.

Load that render onto a one-sided square, connecting it to Alternate_Diffuse and turn off Specular_Value and Diffuse_Value (set to 0). Position the square just inside a window, maybe 8 to 12 inches back, so we see it from outside. Now you can re-render from slightly different camera angles, but they can't be too far from the original angle. Once that looks about right, duplicate the square for the other 7 compartments.

This will work for limited perspectives. If you render several sets from slightly different angles, you should be able to populate even a curved train of many cars - using different angles for each car. 

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