Slick Sloth

Step 1: Add the following to your Agency.xml, right after <Agencies> will work fine. Double check the bolded lines (Your vehicle models)
 
 
Step 2: Next, edit the stations .xml. All of the BCSO stations are currently LSSD controlled, so do a search for any station with "<Agency>lssd</Agency>", and replace "lssd" with "bcso" for any location you wish the BCSO vehicles and people to spawn immediately outside of (Note: They will not be patrolling at this step, however it's extremely useful for step 3)
 
Step 3: Load the game, make sure nothing blows up, and go to one of the stations you changed in step 2, to check if things are spawning their correctly. This step should eliminate step 1 or 2 as being the source of an issue, if things blow up later.
 
Step 4: Edit dutyselection.xml, and add the line "<Agency>bcso</Agency>" between the <Vehicles></vehicles> tags. This will make the vehicles selectable from the garage.
 
 
Step 5: Edit the Regions.xml
 
Blaine County is already set-up as a distinct region in lspdfr 0.4, so all you need to do, is under local patrol, edit <BlaineCounty><Agency>lssd</Agency></BlaineCounty> to read <BlaineCounty><Agency>bcso</Agency></BlaineCounty>
 
 
Now your agency will ambiently spawn in the designated location, and respond as local backup from the back-up menu.
 
 
If you want to get into what edits need to be done for an air unit, or a swat child agency, just let me know. You can also give me a heads up once you figure out the cop models needed, for their relevant edits.
 
 
For the actual cop models themselves, a good source would be to install RDE (Make a copy of your GTAV folder first, RDE has an auto-installer which will destroy your game at the moment, as it is very outdated), extract the bcso cop models from that mod, and then insert them into your copy of GTA.