http://www.minecraftforum.net/forums/mapping-and-modding/minecraft-mods/2524489-realistic-terrain-generation-rtg-realistic-biomes?comment=3217

TechReborn doesn't add biomes, and I can confirm that rubber trees are growing in the biomes they're allowed to (Swamp, Forest, Jungle). Nothing to do here. :)

Good point - I've updated the title to clarify.

RTG has inherent biome support in v2, so this would just involve doing realistic versions of the biomes from TR.

I don't think there's anything we need to do here. TechReborn should be able to decorate biomes with their trees without us doing anything, and we probably shouldn't be customising mod added stuff (and possibly crreating balace issues, etc..).