to expand on the SUGU a little.
Lets look at this map of the 52 and then say each letter is an atom.
So you have 052A to 052N which is what EMS used to create the CAD. For what every reason EMS copied alot of things NYPD did. In FDNY terms think that each of those are a box.
Now bring in SUGU. So if a call comes in from an address in 052F the computer will look at the SUGU string which will say something along the lines of:
052F-052G-052D-052E-052H, etc
So now onto how it picks which unit to assign. Lets say we have EMS units 27A - 27D.
27A is 10-89 which is within 052H
27B is 10-99 at the station in 052E
27C is just going 10-8 from a hospital in 052D
and 27D just drove into 052G to get some food.
GPS will update the units location and atom as the drive around, old days you have to do this by mdt commands.
So now computer see's that 27D is in 052G atom which means they get the run.
Lets also add another EMS only thing. 27D is now on the way to the scene and it's a EDP (non - emergency ) call. 27D is still in service for runs until they go 10-84. So when a call for a cardiac arrest comes in they can be pulled off and assigned to that incident.