Locomotive and coal cars I modeled in Maya nurbs.
Desert floor is a polygonal mesh with USGS Landsat elevation data applied from the Kelso Valley.
I set up the base animation of the camera move with aim constrains. The camera always aimed at the locomotive as I manualy placed of the camera in the scene based on the timing to the music that I wanted. Then I baked the animation curves, and then fine tuned the curves quite a bit. Errrr... quite a bit.
Bushes are rendered via a custom MEL script I wrote, vSprites. I estimate there are around 60,000 bushes in this animation. The scene is manageable since vSprites generates and culls bushes on the fly during render time. Each vSprite is a single polygonal plane facing the camera with a small file based texture from an on-demand and once-rendered Maya scene with 1 Maya Paint Effects-based bush object (though the object scenes could be any geometry). ( What a mouthful - still, easier to say than to make :-). Bushes within a certain range of the camera are re-rendered each frame to maintain realistic 3d perspective.
7 render passes: Locomotive, Coal cars, Locomotive shadow, Coal car shadow, Steam, Heat Diffusion, Desert Floor.
Rendered in Maya. Comped in Shake and After Effects. Compressed to Sorenson Codec with Quicktime pro.