LoadLevelAsync Question

I was planning on using LoadLevelAsync to stream in terrain patches but wanted to find out what happens with shared assets. For example, if all of my patches use the same 4 textures will copies of those textures be made every time a patch is streamed in or will unity see that the textures were already loaded from a previous patch and not reload them? I'm aware of the push/pop dependency API but wanted to find out if this applies to streamed scenes as well.

The reason I ask is that terrain patches are going to have quite a few assets in common, buildings, textures, rocks, trees, etc. and it seems extremely tedious to have to design a build process to deal with dependencies for terrain that could have quite a few patches. What i would love to do (which may not be possible) is simply create my streamed scenes and worry about how to stream them into the game while letting Unity worry about dependencies.

Is there a better way to think about this or is this the typical problem people have to deal with when streaming terrain?