Hard Reset for instance had MLAA as the post AA option before switching over to FXAA in a later patch. Developers can implement MLAA in their games just like FXAA. MLAA is not specific to AMD cards just like FXAA. AMD implemented it in their drivers using Directcompute by leverage the modern GPUs ability to do more general processing work (which is why it is only available on the newer AMD GPUs). The reason was to showcase the ability for the CPU to do AA.
MLAA is actually a technique first demonstrated by Intel (not sure if it was entirely developed by them or not).
