What ever cellular game camera you get, I wouldn't plan forward for more than 2 years. Cell phone technology is changing at a rapid pace. In 3 or 4 years GSM or CDMA may not be available with any of the big carriers. In other words, It's kind of a crap shoot right now. Things may change or they may not.
For now, go to this web site: http://www.wirelessadvisor.com/
and type in a zip code to see what services are offered in that area. Some places in OKLA don't have GSM in 850 MHz but do in 1900 MHz. 850 goes a lot greater distance than 1900.
Once you find a carrier with the service you want, then you have to determine if they have a cell tower that can be seen from your particular area with a useable signal strength. Also remember that as leaves start falling signal strength in general will start going up in the fringe areas.