I've got one on an older frame I'm not using at the mo and it's very similar in size to a standard 1" HS.
Admittedly I've not changed the bearings. But I fitted it (and the one on my friend's bike) and there is no way it uses the same bearings as a 1 1/8" HS.
It's not a physical impossibility, but the 1" cups would look huge, like the bottom half of an FSA Pig