Think of the BES as just a gateway. When you attempt to make a network connection, if the address is reachable by the BES, then it will be reachable by the device.
For example, if you attempt to connect to internalserver.mycompany.com, that connection will only work on devices configured to use your BES. It won't work on a device configured to use someone else's BES, because their BES won't be able to resolve the address.
This is useful because it allows you to extend your internal network to wireless devices without having to expose those internal servers to the public internet.
That said, all you are doing on the device is making a network connection and getting the result (InputStream). It doesn't necessarily need to be a real web service, but your comment seemed to imply you are trying to call methods in classes on the server. If that's the case, you need to rethink your architecture. If that's not the case, just ignore this paragraph.