Game uses nvidia's FXAA for edge aa.. Same technique is going to be used on Battlefield 3 too..

Such a technique is quite a novelty in the video game industry and it’s very likely Crytek will release improved versions as it has potential to also be merged with different techniques - for example, it’s currently also combined with Nvidia’s FXAA in “Extreme” spec, in order to improve quality further with sub-pixel accuracy results from post MSAA
http://crytek.com/sites/default/file...es_final_2.pdf