They work by giving you a small discount on a new camera or camera lens combination, 5-15%, something like that. I've used it at least twice when the discount was 20%.
Basically, you give them the model and serial number of your broken camera. They then offer a discount on the new one, that includes refurbished ones. They send you a prepaid return box or envelope for the old one. When I did it, it had the address of a recycle place. Once, they told me to just trash it.
I used to pickup broken old cheapo rebel SLR's at garage sales for a dollar. Then, when I wanted a camera, I called with the serial number of one. I have a couple of them around I think. The discount is not significant now. I get 10% off thru my employee discount plan, or a sales tax rebate from B&H which is about the same.
Call them and ask. I've heard that they are offering a bit higher discounts than they were 5 years ago when I stopped using the program.