There are two situations here... the local AFS provides cover for normal operations so, if there are to be no emergencies, all should be OK. However , it's obvious that a local AFS could not cope with a major emergency which is why outside services attend for certain categories of emergency.
The question needs to be asked whether normal operations can continue if that outside cover is not available in case of a major emergency.
Perhaps someone with a greater knowledge of the safety services could respond?