This CellTower Locator uses the location area code and CellID or SID/NID/BID to determine the location of your nearby cell phone towers. Each base station covers a certain area, the more cell towers in your area, the more accurate result it will return. So the density of cell towers will determine the accuracy.
Generally, the density is higher in the urban areas especially at downtown. While in suburb areas, each cell tower covers a wider area, so the result is less accurate.
This CellTower Locator sends query to Google location server, and returns the location. If the data are not included in their databases, no results will be returned.