Yup, they're glued in place. Apple used some pretty serious adhesive to hold them in, but it's nothing that a heat gun wont soften. Picking them out from the back is not possible, so you have to heat them up then push them out from the inside. The main problem with removing them is that you have to remove just about every other component in the iPhone to get to them, which is a real pain.
Heard anything to the effect of using a form of glass chip repair to fill in a cracked/chipped glas back panel on iphone 5?
Similiar to how a chip is repaired on the windshields on cars and trucks these days. Basically a form of epoxy and on quarter size chips and smaller a suction cup style plunger combination is used to inject the epoxy into the cracks.