I worked at Mobilink until a week ago.
Here's how it works:
Sites (Cell Towers) are characterized by how much revenue they generate, and the ones that generate the highest revenues for the company are known as platinum sites. These sites have priorities for everything, including upgrades, emergency repairs, you know the whole shabang. As far as minor cities are considered, there are no plans as of yet for the expansion of 3G, since there aren't simply enough users to justify spending money on equipment, service, repairs etc. So don't hold your breath, it's not happening anytime soon dude. Not unless more and more users start using mobile internet in these cities to increase demand, and make achievable revenues enough to justify upgrading to 3G. There are a lot of other technical issues that go into making a decision like this, but this is the most important one and the simplest to explain.