Unfortunately he may not be able to use extralegal resources, and he was the head of agencies that did the work to which you refer, not the person who did it, most likely. But he certainly knows who to contract. Hard to know how focused the company really is on that detail.
Though I agree, that's the reason to be excited about his appointment. He likely can track them down through both white hat / legal means and probably also through black hat / extra legal means, though he can't use any black hat info legally. If they were using black hat means, they'd probably know everyone they are in contact with too.
Hard to know, but I would expect he'd keep it all white hat. But you never know.
And if they were aware of other illegal activities, a few anonymous tips would be all it would take. Boom. They'd never know why or what or how.