A little bit off-topic, but what adds that lush grass that can be seen in the demonstration pictures?

That is Green Pita! It's a decorative from the base game that normally isn't available for use, but with the map editor from the mod Editor Extensions, I am able to select it from a list, configure the shape and size of a brush, and then "paint" it onto the ground until the area is saturated. So adding it unfortunately relies on a "cheat mod", but at least this particular use of the mod has no impact on game play. (I wish the game had more in the way of agricultural fields & green decorations, because I really like the beautiful contrast it can provide to "grungy" industry and infrastructure.)

So there are no mods that add it normally?

No, not to my knowledge, unfortunately!