When it comes to military aircraft, the situation there is kind of interesting. There's no general exception for the military, military aircraft are generally "required" to transmit ADS-B unless they have a specific reason not to (and I believe this requires authorization from somewhere up the chain of command). I put "required" in scare quotes though as many military aircraft are simply not equipped... the DoD has drug its feet on installing ADS-B out and the FAA has basically relented by setting very lax objectives. FAA requested DoD to have ADS-B installed on 21% of aircraft by the first of this year and I believe they met that goal... but it's still less than a quarter.
Over time more and more military aircraft should be appearing in ADS-B data, but I suspect it's going to be some years before it's almost all of them.