In ABQ, the main private company positions its ambulances strategically around the metro area based on where traffic accidents are likely to happen (based on statistics).
They choose which emergency room to transport to based first on medical condition. Trauma, for example, nearly always goes to the hospital with the trauma center. Other factors might be which ER is closer, which is able to accept patients, and patient preference.
In Lincoln County, NM, which is geographically large and has a very small population, the county has contracted out ambulance services to the local hospital. The hospital maintains a main ambulance station at the hospital and satellite stations in a few of the smaller communities around the county. The Mescalero Apache reservation is also covered by this service. Both paid & volunteer responders staff the service & respond to calls, and it can take 20–30 minutes to arrive on scene. Occassionally(sp?), they will transport to ABQ or El Paso.