According to some of the articles I've read, the issue of Greco, Limone, Tameleo and Salvati came up more than once over the intervening years, so I'm finding it hard to believe that the agents' superiors would have been ignorant of the case.
Even if they were that of course does not alter the fact that the agents were being rewarded while the four men they helped frame for murder were in jail. Which means that those who did know about the case, whoever they were, did nothing to stop the agents from being rewarded.