When I import animations from Maya, I bake all the keys for all objects and save the file to Maya Binary format, but I get lots of problems when I play the animations, f.e if I do animation with replacing technique , like replacing the mouth in one frame when I play the animation in Unity the animation will play some inbetween frame that shows the mouth dislocated. I guess this is because Unity is playing the animation based on time and not on frame, but is there a way to make it Snap to a frame?

In Maya, the way to achieve this is to make all keys Stepped which means no interpolation between frames all transformation remain static until next keyframe is reached. but Unity (at least Unity iPhone) does not recognize this kind of interpolation.