In the German forum 3DCenter, the user Blaire found out that FS-SSAA possibly works via transparency antialiasing.
Restrictions suspected/known so far:
- OpenGL, DX10 and DX11
- 2x, 4x and 8x (TR)SG-SSAA/(TR)RG-SSAA - not sure yet what grid is used
- the number of SSAA samples must not be greater than the number of MSAA samples
i.e. 4xMSAA+4xTRSSAA=yay!, 4xMSAA+8xTRSSAA=nay!
- as of now works only on GF 400 (Fermi)
- in one case (Just Cause 2), the number of SSAA samples and color Samples have to be the same
- so far, it is not possible to adjust the LOD accordingly in DX10+. The image gets a bit blurry. This can be alleviated by choosing only 2xTRSSAA
The whole thing seems to be a bug. The magazine PC Games Hardware (PCGH) has contacted Nvidia about this and is awaiting a response. Possibly, Nvidia is experimenting with SSAA in their drivers and it got messed up somehow.
Although the article below is in German, you may enjoy the screenshots it contains which prove SSAA actually works:
Personally, I think this is great as you cannot force or enhance AA in DX10+. Flickering/shimmering shaders cannot be countered in DX10+ apps, unless SSAA is explicitly built into the game (Arma 2 for example).