IIRC, they don't have a cellular radio in the vehicle (or even a FM radio). All the connectivity is done via Bluetooth with a mobile app.
It's been a while since I read up on them and things might have changed, but I have a lot respect for what they're doing. Full embracing right to repair and customer privacy when the entire industry is moving at lightning speed in the opposite direction.
Aren't their companies that are doing their telemetry over bluetooth bridge to phone' internet? Not saying slate necessarily does, but it's certainly an available exfil surface, especially if there's a 'manage your slate vehicle' app.