You're never under any obligation to speak to PIU or their federal agent friends, no matter what the contract says. They are criminal investigators not internal investigators. If they try to fire you for refusing to speak to them, there's no chance in hell the courts will view that as anything but coercion and a 5th amendment violation. They can fire you for not speaking to PSU, however we all know PSU and PIU share information, so you could probably have that part of the contract stricken in a