Technically, yes it's possible to get the "unrestricted access to internet". Realistically, looking at the "speeds" in question, those guys are simply over-pitching their product.
For a good part of this year, I had the opportunity to tinker with a similar product from http://www.wi-free.com. That was before they stopped selling their vouchers directly to users and most importantly, before they revamped their website & going full throttle into VPN business ;)
The idea back then was very simple : making use of some commonly open ports on any Telecomm Opco who would allow you to latch onto their data network regardless of your account balance. Some light-weight software running on your local PC would then make use of any open DNS, ICMP, TCP or UDP ports on the Opco's network to talk to the wi-free servers that in turn got you onto the internet.
Speeds were as erratic as they came, depending on the protocol and the physical location of the proxy servers. On a good day, I'd manage to stream a few random videos (especially KTN livecasts) reasonably well while torrenting in the back-ground. Too bad I never bothered to benchmark the erratic speeds.
Gauging from the online fora at the time, the wi-free service was more of a hit in Uganda and Indonesia than in Kenya.