Most servers don't use these, but to somebody, they make the OTA whitelist more interesting.
Tasked of guarding the office of the administrator, the Sectorial Commander, or the Commander. They also guard the outskirts of any given city to scout for resistance activity. Usually these units are flagged up the most.
Standard OTA division. They are normally the ones deployed when some sort of crisis is occuring, otherwise, they are in the stasis most of the time.
Pilot hunter-choppers and gunships, again, rarely deployed. These units generally NEVER come out for any type of ground assault.
King (EOW only) Edit
This division is for the Elite OverWatch. Kings' are highly trained overwatch units. They generally are the ones to lead squads of standard overwatch units (I.E. Echo)
Overwatch Sniper. Deployed to assasinate rebel targets. Usually these units never come out or are rarely seen.
Most servers use Ghost as an MPF division, but it makes more sense with OTA. These units are deployed for stealth missions, where their deadly accuracy and efficency are required. These units receive special training to use the Combine Sniper Rifle, along with the Ranger division.
These units made up all of the shotgunner units in the Transhuman Arm. Serving at both Nova Prospekt and inside the city. They are used for aggressive and executive breaching techniques, being armed with close-combat weapons. They carry Flash grenades and occasionally led the squads of OTA into the sewers, located as team leaders on Fireteam unless a KING is present.