I was told by R’ Matisyahu Salomon that if a person really did commit the crime, there is no mitzvah of pidyon shevuyim. Pollard did commit the crime.
As for his plea deal, the government did not follow it because neither did Pollard. Part of the deal was that he wasn’t allowed to speak to anyone about the case whatsoever. Shortly after, (before the sentencing,) he granted an interview. He actually violated the deal first.