Departments are awarded based on need, not who has and has not gotten money in the past. That is not to say that one department has a greater need than another department. At that point, your skill in writing the grant and expressing your need comes out. One grant may not cover all the needs for that department, and that might be why they are getting more than one grant (such as the case with my departmennt). Also, the needs might be in different areas (i.e. vehicle, FF ops, EMS).
I don't understand why the same departments keep getting the money. If the government wants to spread the funds out, they sure are not keeping very good records of who is and who isn't getting the money