That's Kurt's work, he does a lot of texturing work for the studio in Substance Designer.
When creating the environments the artist will make sure the UVs are tileable for whichever parts we know are going to have these textures applied. I'm not sure how large a space in Evolve these were, but ultimately they can be as big as you can without losing details because there is a limit.
These are PBR sets so they have multiple maps applied and (I think) it's a height map that's made so that it doesn't appear flat. Then of course there are the set-dressing pieces that are added on top of the ground like plants, rocks, trees, etc.