If going from wing spoiler to lip, holes from the wing spoiler would need to be filled.
But to answer the original question, Jays6's dealership is right when they say it cannot be done. There is no lip for the hatch (because they all come with the wing spoiler in US-spec), and the sedan's decklid profile around the lip spoiler area is actually quite a different shape than the hatch. Plus, the brake lights from the sedan's lip spoiler would look really bad on the hatch because they would never turn on.
If you really want a lip on the hatch, you'll need to go aftermarket (and even then, you'll likely need to fill in the holes from the original wing spoiler).