I think I can explain this, although I'm not German(Scottish actually), Werkfeuerwehr is a works fire brigade like at factories or chemical plants, Betriebsfeuerwehr, I think you acually mean Berufsfeuerwehr, which is the professional firefighters that are paid to be fire fighters and are more commonly found in the main cities and that brings it to the other fire service in Germany, Freiwillige Feuerwehr, which is the volunteer firefighters that are all over the country.
OK gents, some of you were very close. Berufsfeuerwehr = Fulltime/professional FS Freiwillige feuerwehr = Retained/volunteer FS Werkfeuerwehr = works FS fulltime (like those big chemical plants, airports etc.) Betriebsfeuerwehr = works fire brigade (volunteer)such as small factories, hospitals etc. those employers who do the fire-fighting as a second "job"
Just to note that retained firefighters in the UK are actually paid, while German (and other counties')volunteers are not. This absence of payroll expense means that services which rely on unpaid volunteers tend to have larger budgets for other expenses.
Added by Bob on 04 April 2009.