Offering Tor or VPN services over-the-top of a normal Internet connection is the most common way for people to connect, however misconfigurations and exploits can result in leaked meta data or clear net browsing that can compromise your privacy.
The Onion3G design is a closed network between your 3G device/MiFi/modem and the Brass Horn Comms Tor bridges, this may make the collection of Internet Connection Records (and by extension other forms of bulk surveillance) less effective.
This is achieved by only issuing private IP addresses to remote endpoints which if ‘leaked’ won’t identify you or Brass Horn Communications as your ISP. (Furthermore your computers aren’t technically connected to the Internet so can’t communicate to the servers that the exploits need to connect to in order to leak your address.).