Ready to respond and staffed at any given time. That is for a city of 100,000 people plus they cover Vineyard too.
Imagine when there is a major catastrophe in the area and dozens are injured. Gonna take awhile for ambulances to transport to hospitals and they will have to come from all over the valley to help. I’ve seen fire trucks from several different cities respond to incidents in Orem and Provo when things get hairy at once (large fire and an accident or two at the same time)