The first thing that pops up in my mind is Westmed Ambulance in the East and South Bay in California (eg Hayward, San Jose). I've seen them, but I don't know about their hiring process.
OP, there are a million ambulance companies and a lot of them have similar names. Even if it is a large company (eg AMR, Rural/Metro, Falck), it doesn't mean that they don't operate different in different areas. Be specific more specific about your location. Usually people will say the county or city name.