As far as I can tell Onavo is more of an HTTP proxy than a true VPN connection. A true and full VPN connection would mask/change/hide your public IP adress from Verizon, AT&T, etc. Onavo's "VPN connection" does not do this entirely. If you use a network tool like LANDroid (found on Google Play), it'll show your IP assigned by your carrier (indicating there is no VPN connection). However, if you head to www.ipchicken.com via a web browser on your phone it will show an entirely different IP address. This is what leaves me to believe it is set up as an HTTP proxy. The LANDroid program is gathering your IP without using the HTTP protocol and therefore routes through your standard carrier IP (like your web beowser would without Onavo even installed, or just turned off).
Now since I am speculating off of a very simple IP check here I don't want to leave out the possibility of an advanced configuration on Onavo's VPN servers. It could technically be a VPN connection but only routing HTTP traffic via the VPN connection.
Saw your question as I was looking for the same bits of information... months later you get an answer