The cost of something like that would be staggering, and tends to be similar to hanging access points, plus the cost of cellular broadband. You can check with the cell carriers (AT&T does offer such a service, not sure about the others)
My understanding is that the point of this service is more about having better cell coverage than it is about wireless internet access, and it would give them internet access, but not access to your network. If you are looking for local network access, something like the Cisco Aironet series is the way to go. If you just need internet access, either would work, I still fell that wi-fi is a better option, unless you need to improve cell reception at the same time.
