Pretty sure someone on this forum has done exactly that, or at least played with it a bit but I can't seem to find it. If I remember correctly though, they couldn't get it to fit right and was having some issues getting stuff to line up. I also think I recall that because the Impreza bumpers are not as long, he had to pull the front bumper beam off to push the bumper cover back so that it lines up with the wheel arch. I think that's also what is happening in the picture you posted. As long as you don't mind your factory headlights and stuff having a bit of a funny gap below them where the bumper should meet up, you could get crafty with some zipties to hold it on, but I really doubt there's really a solid way of swapping to the RS bumper cover since you'd need to remove the bumper beam and that's pretty much what supports our factory bumpers.

Can't comment on the JDM fogs though, I've never looked at them in person and I run the stock Outback bumper.