Nv has release candidate version of the game. It didn't had Treesfx in it, but they got that aswell eventually. They could optimize everything. They didn't get much time to work with treesfx, but they did get the source code.The podcast from last year where nVidia accoused AMD that Eidos wasnt allowed by contract to support nVidia with the release version of the game prior the launch.
Not even remotely close to Gameworks closed libraries with the contract that forbids any optimizations for amd hardware to be done.