System for providing alert-based communication services for which corresponding alert conditions to be met by mobile stations are defined. The system includes an alert engine capable of firing alerts associated with the alert-based communication services if location data regarding the mobile stations is indicative of the mobile stations meeting the alert conditions corresponding to the alert-based communication services. A requirements engine determines an expected earliest future time at which at least one alert condition is capable of being met by a particular mobile station and outputs a data element indicative of a requirement to obtain updated location data about the particular mobile station in advance of the expected earliest future time. A scheduler receives expiry times data and processes the expiry times data for determining an order for servicing the location requests.