Hello,
Recently I have started to whit creating and recreating worlds in CAW. Right now I am working on new version of Bridgeport and I would like to add military base and police department there which is separated from city hall. therefore I would like to change the Public Service Office lot function to be just City hall and not all three combined but I can not figure it out.
How do I do this?
Also I would like to know how to create them.

Replace the Bridgeport RH with a City Hall from another town that serves as only that, such as one from SV or Twinbrook.

I know I can do that, but I would like to use same model of building as original one from Bridgeport. Isn't there some way to do that or some mod with version of the building that is just city hall?

It was certainly answered before, but yes, you can change the type of a pre-existing Rabbithole.

1) Using S3OC, you'll have to look for the combo RH of Bridgeport, click clone or fix, give it a new name and description if you like, don't forget to tick Renumber/Rename internally and click start to clone it.
2) With S3PE, you'll have to edit the OBJK (right click Edit OBJK or click Grid at the bottom) and change the rabbithole type from Sims3.Gameplay.Objects.RabbitHoles.ComboCityhallPoliceMilitary to Sims3.Gameplay.Objects.RabbitHoles.CityHall, save the changes and save your package. You're done!

When you place your package in your Mods/Packages folder, it should show up in game as a new rabbithole with all the options for the City Hall only.