To a point, yes. Before cell phones were starting to get popular, getting access to the SS7 network required very expensive telco equipment. So somewhere along the lines, the telcos setup what I call Gateways, using the SIGTRAN layer, where all of the lower layer protocols is just a packet payload as far as the internet is concerned. This significantly reduced the cost for smaller telcos to get in the game. It wouldn't surprise me of some African Native village can have their own Cell tower (OpenBTS), interfaced to an Asterisk box connected via the internet to an SS7 gateway. There was one setup at Burning Man in 2013, and at one of the Defcons of past years setup a "tower". Obviously there is more to it then that, but these would be the major components.