The use of probability — i.e., invoking 'likely results' and assessment of odds — hides the deeper philosophical issue at stake. This issue boils down to the following:
Are all acts ethical if one isn't caught committing them?
This is a commonly-held position in the practical world, one that ethicists and theologians have fought against for as far back as one cares to look. The logic behind it is simple enough. Everyone believes that their own intentions are good; everyone believes that their own action are either justifiable or excusable; everyone believes that they themselves are exempt (in given context) from the vague, impersonal, didactic, and sometimes irrational rules imposed by society. Thus there is a strong inclination to believe that one's own actions are moral by default, and that the only concern is hiding one's actions from those who might ignorantly try to punish them.
This is as true of CEOs and state leaders as it is of bricklayers and baristas; as prevalent among saintly grandmothers as among serial killers. No one does something they themselves think is wrong, but they are much more fluid about what other people think is wrong.
None of the major schools of ethics would condone the agency's actions. Consequentialists would point out that bad consequences exist — e.g., the transformation of an agency of justice into a criminal gang — whether or not they are known to the public. Deontologists would say that it is irrational for the agency to pursue criminals while excusing their own criminal acts; that is not a uniform or universal principle. Virtue ethicists would point out that the ideal of criminal justice precludes the commission of criminal acts. Whether they can get anyone to listen is a different matter, but the ethics of the situation is clear for anyone who thinks philosophically.
It would be an interesting and disturbing world if ethics were a subfield of quantum mechanics, ethical considerations only occur if an act is externally observed (unless the moral wave function collapses, good and bad remain superimposed on the act). But I'm not sure the world is ready for the introduction of that kind of scientific nihilism.