I haven't heard about this officially from them, but my company buys back tens of thousands of broken LCD screens from repair centers around the US and abroad so I know there is alot of value in them. For example, this week (price can change fast) we're paying $55 for iPhone 5 cracked LCD screen. Thats for the LCD screen only as long as it has a good LCD.
I don't think apple does this though.
Also a helpful hint: If the crack is small enough (just one line) then I think apple will replace the screen free of charge under 1 year warranty.
I also did hear that previously they just swapped out a new phone if you had broken screen but that they've already begun to replace just the LCD in the store.
If any repair shops are interested in selling their broken screens they could feel free to check out my profile which has link to our website.