Well really that's just a standard tree, using flat plains to represent the leaves, but probably billboarded so they always face the camera. You could get a basic trunc and place lots of textured plains at the top then orientate them to the camera each loop.
Texturing the leaves is really a case of getting layers of leaves, fading into darker green. I would make some leaf brushes and reduce the cover and darkness to mimic the BF:Heroes look.
When I made my trees, I did something similar, only I used oversized leaves, they kinda remind me of fuzzy felt - which was something we used in school when we were kids...
The brown leaves fall off the tree as it sways back and forth in the wind - I went that route because when I tried to make a real tree, it looked like crud, and didn't want to just steal one. It was very straightforward to make those trees, with some more time, I think it would be possible to make tree's like in BF:Heroes with the same techniques.