Once the P/P shares become unrestricted they are the same as any other common share so why shouldn't they be able to cover a short position?
The only rub that irks longs is that they are able to attain these shares without having to buy them on the open market where normally the volume of such a buy would raise the share price considerably.
Many find this route distasteful, but compared to other shenanigans allowed on Wall St this is probably one of the least distasteful ploys.
You can if you don't get caught. This P/P had no hold on the shares and that was what the shorts were after with the brokerage firm. This deal was a registered direct equity offering so they would have free and clear.