“I hope they did not do something stupid like granting him immunity before they know what he is going to say.”
It’s standard procedures to require the person being granted immunity offer a “proffer” which outlines the content of the testimony that will be provided. Such a “proffer” cannot be used against the individual. The immunity can be withdrawn should the individual renege on the “proffer”. IOW, the feds already know what the guy will say.
that is what we HOPE has happened.