The whole purpose of the PPIP system is about increasing the price of the trash securities so that the troubled banks can dispose of the trash and remain solvent.
Unforunately for the government, the PPIP is still structured such that the private entity might take a loss and therefore will not bid up the trash securities enough to make the troubled banks whole. The only way it will work is if the banks game the system by setting up sock puppets to buy their own trash (with government money) at inflated prices.
The thing is, this is just business as usual for wall street.