The report in theURL points to growth in GSM use in Latin America due to the decline in TDMA. The last paragraph of the report is significant, and why both AT&T wireless and Cingular (prior to their merger) independently chose to migrate to GSM from TDMA (and not CDMA) -- cheaper handsets. This is primarily because GSM is a simpler technology, therefore cheaper to implement. Scale economies also play a role, as GSM has the larger market share worldwide by a large margin (over CDMA).
The primary advantage of migrating from TDMA to CDMA is that the migration to 3G is less disruptive and (potentially) less expensive for the service providers.