Is the camera in the new iPad using "4S optics"?
No, the iPhone 4S has an 8mp camera.

The prior iPhone 4 had a 5mp camera though.

But, yes, the older iPad had a much worse camera - less than 1mp.

This would seem to show it's from the iPhone 4: The new iPad camera: we've seen it somewhere before

Megapixels aren't everything - but the new iPad certainly has the best camera in an iPad so far. The front facing camera isn't that great though, even with the rear one hugely improved.