I think that whomever issued the belts, they did it to further their own (Nemesis) agenda, not as a benefit to the FBI agents. The EK seems to me to be way too independent to be a Nemesis tool or infected. The belts were tainted, they drove the agents to act against their training and conditioning, I'd go with either Cowl, or a mole in the EK's court, maybe Rafforut.