This is off topic for this thread, but I will answer your question. (This is an amateur radio forum).
They are on the Ohio MARCS system which is a Motorola Type II system using digital voice. It has always been difficult to decode on a scanner. This is an old system and is being replaced by the new MARCS-IP P25 system which sounds great on a scanner (until they start using Phase II).
Make sure you have it programmed as custom/rebanded and I recommend an 800 MHz. antenna.