The positioning service is directly related to the device and its own implementation to find the position assumed by and from the various method that was used to find the best matching. It does not seem to be directly related to Bing API in this specific case.
In order to improve positioning speed and precision, the different systems can switch to Wifi-Positioning to other method like A-GPS or even cell identification.
If you try to get the information about your position based on your wifi, on Android, we can easily assume that it will used the Wifi-cell as the position that means that the known location would be the one retrieve from various crowdsourced information from your own devices and also others. That said, in WiFi, you will not be moving, you are connected to the Wifi cell without any other information.
If you cannot get your position in 3G, try to go outside so it can use the most precise positioning method (A-GPS) as it appears that phone cell-id is not working in your area.