I wonder if they've made the device smarter about being used outside of a vehicle?
From the TAC:
Device restrictions: For in-car use only. Telematics req'd. AT&T reserves right to terminate service if device is plugged into anything other than a vehicle.
Sounds to me like they've programmed the device to read diagnostic data from the vehicle to confirm compliant usage?
A review website indicates the Spark service is $30/mo, and the hotspot is configured to shutdown after 30 minutes after the vehicle becomes stationary... so you can't park your rig and use wifi all night long?