To me it seems low. I used to work on many residential projects in California. While the police protection was typically measured in an officer to population ration (i.e. 1 officer per 1,000 residents [this was a good ratio]) fire services were evaluated based on response time.
If I remember correctly, Los Angeles County Fire Department (LACFD) used an average travel speed of 38 miles per hour during a response. The maximum allowed response time was somewhere about 5 minutes. So ball parking it, factoring in turn out time, you had to have a station able to serve a given area within 2 miles. This ofcourse figuring the distance an engine/truck/ambulance could travel at 38 miles per hour in 5 minutes.
With that being said, three firefighters for 11,000 people seems low. Especially considering town with 11,000 people are usually fairly rural so the area in which they live would be expanded compared to the burbs.