9 to 5 Mac reports that a spokesperson for T-Mobile USA has disclosed the carrier currently has over one million iPhone users on its network, despite the fact that Apple has not offered an unlocked iPhone in the United States until the past several weeks and that differences between T-Mobile's network and other GSM networks that mean that iPhones are unable to run at 3G speeds on T-Mobile.
In a meeting with T-Mobile spokespeople today ahead of the NYC Pepcom event, I received word that there are actively over a million Apple iPhones currently on T-Mobile's network. When asked for a breakdown, the spokesman said the majority were pre-iPhone 4 but that a significant amount of people had "taken the scissors" to their T-Mobile SIM cards. T-Mobile doesn't currently offer a Micro-SIM solution for Apple's iPhone 4 so people who want to use the iPhone 4 must modify their SIMs into MicroSIMs.
T-Mobile noted that it is planning to roll out micro-SIMs at some unspecified time in the future, but declined to discuss any possibility of the iPhone coming directly to the carrier's network.
AT&T announced back in March that it planned to acquire T-Mobile for $39 billion, although federal regulators are still assessing the impact of the potential merger before giving a final go-ahead on the plans.