I Understand that a Jew is not allowed to ask a Gentile to do work for him specifically on Shabbat.
Thus, one cannot bring a car to the Gentile mechanic on Friday and tell him specifically, "Fix my car, tomorrow, because I will need it Sat. night."
However, a Jew is allowed to violate Shabbat for his or someone else's life-threatening situations.
So let's say Hatzalah (the Jewish ambulance corp) has two ambulances. If an emergency occurred on Shabbat, they have one that they can use, but, having both available obviously, makes things more efficient. as it's certainly possible to have multiple emergencies at the same time.
One ambulance broke down just before Shabbat. The Jew brings the ambulance to the Gentile mechanic and tells him, "I need you to fix this on Shabbat, and call me as soon as you can, because we need it pronto."
Is this a "life threatening" situation exemption that would allow the Gentile to do the work? Furthermore, when the ambulance is fixed, can another Jewish Hatzalah member drive someone on Shabbat to the mechanic so that he can get the ambulance?
To ponder: At the moment, no life threatening situation exists (not even a doubtful one). But, an ambulance needs to always be ready.