Here's the latest of 3D-heavy tracks I've completed:
Anim8or-only:
http://www.coastercrazy.com/track_exchange/detail/11170
Mix of Anim8or and 3DS Max (Anim8or for ferris wheel and 3DS for mostly everything else):
http://www.coastercrazy.com/track_exchange/detail/16070
I never got Anim8or to work with .png's; it simply refuses to load the texture last time I tried. I've also had to deal with a smooth shading issue with cylinders before, but lately I've seen the same issue come up on 3DS Max exported models too. (The issue is where there is a seam along the cylinder which creates a point where it isn't smooth shaded.) Of course, as evident in the first track, I've been putting environment maps to good use lately. The ferris wheel needs some work in 3DS Max though (mostly to optimize the lights and weld some vertices together), which I'll have to take care of sometime.
If you can get Anim8or to work with .png's, or perhaps get Sketchup to export it and trust Anim8or to leave it alone as you sort out the materials, you can save a lot of polys not just on fences but on many other objects. In fact, I don't see how it's possible at all to make trees without alpha-masked textures; you have to use NL's default tree system by editing the environment file or you end up with a .3ds that either looks bad, uses way too many polys, or both.
My upcoming project will be about as 3D object dependent as the first track linked above was, but everything is done at considerably better quality than before; higher res textures and better techniques and optimization using alpha blended and masked textures as well as lights and sounds. The project's object folder is 58mb now, which includes both source files and release files which I'll need to sort out soon.