To make sense, the discount would have to be more than the likely second-hand price, otherwise, if people could get a better price on online auctions, there would be no incentive to use it. The advantage for Canon would be that, by offering such a service, they would be taking these EF-M lenses out of circulation, making it harder for EOS M users to continue to obtain the parts which might keep them in the EOS M system.
Thinking about it, though, the administrative cost and other overheads might well outweigh the benefit Canon might reckon to gain, so I think “snowball’s chance in Hell” could be right. I’ve no idea if there’s any precedent in the camera market.