That is an interesting thought but definitely not possible.So, the first optimization that come to my mind was to render the four textures to a mrt in one pass (which saves lots of draw calls)
Take a look (I borrowed duststorm's screenshot from the first page): http://www.ogre3d.org/forums/download/file.php?id=4486
The geometry positions in relation to the camera are different on each cascade.
What MRT can do is assign different colors to different outputs, but the rendered geometry itself is the same on all targets (they all render with the same camera).