Last year when Entune hadn't worked for me for four months (!) because of various incompatibilities with new versions of Android, I was frustrated enough to reach out to Andy Tweddle, the head of the Tweddle Group.
Andy sent me back a very nice note that while the Tweddle Group originally built and provided support for Entune, they had divested Entune's operations to Nuance (http://www.nuance.com), who now sell an Entune-like solution to the automotive market. Tweddle no longer has any stake in Entune, so I would recommend that future angry letters end up going to Nuance.
It is fair to say that the Entune components update over the air, however. The Entune-related apps in the car will update through the Entune app running on your phone when your phone is connected via Bluetooth. The application on your phone itself is updated through iTunes or the Google Play. Connectivity to your car through the service is handled remotely as well. It would seem to one thing you wouldn't need to take into the dealer for service, unless there was a problem with communication to/from the car because of an issue with the SIM card or radio hardware in the ECU gateway.