Ill say speaking for my own community, the local government employed a system where they would accept otherwise unwanted vehicles and in some cases pay a little scratch for them, to get them out of yards and and lots etc. Granted the circumstances of doing it on a scale of a few hundred cars compared to potentially a million or something cars is a totally different deal. Also the motivation behind the programs are two very different concerns.
As for the national one, unfortunately, I dont think it will meet its goals. But they never do, doesnt matter which party is in control. Its the huge secret flaw in Congress..... Dual party partisanship.
On the local scale we were able to exctract about 200 vehicles that for various reasons were unwanted and were in most cases put to good use. The school district took a number of them to use in shop classes and the like.
Others were turned into levy material for some erosion control. Then nearly a barge full were shipped to Seattle for scrap. In the end it didnt make any money, but wasnt all that expensive, mostly administrative costs. Largely it paid for itself.
When the EPA called to complain that the cars couldnt be use for levy works, we told them to go to hell, and won. I know it seems more rare than a blue tiger, but there is some history of success to these efforts.
National level, its probably an impossible job to manage, and I wouldnt want to be the poor sap who has to deal with that. It really depends on the return from the clunkers.