Can you say MetroPCS iPhone? T-Mobile sure can

One of the unstated benefits of T-Mobile’s proposed merger with MetroPCS(s pcs) is one that T-Mo’s customers have been clamoring over for years: the iPhone(s aapl). T-Mobile is already on a technology trajectory that will make its network compatible with the iPhone 5’s fickle radios. But tying up with MetroPCS will get T-Mobile there a lot faster.

The iPhone 5 requires T-Mobile to support two common frequency configurations: 3G in the 1900 MHz PCS band and LTE in the 1700 MHz/2100 MHz Advanced Wireless Service (AWS) band. T-Mobile has neither today, but it will meet the first requirement shortly as it completes the relocation of its HSPA+ network this and early next year. As for LTE, T-Mobile won’t have a commercial network ready until the second half of 2013 and even then it won’t have a sizable LTE footprint until 2014. That’s where MetroPCS comes in.

MetroPCS has a live LTE network in 14 cities, and for the most part it’s running on the same AWS frequencies already supported in the AT&T/Canadian variant of the iPhone 5. T-Mobile CEO John Legere said on Wednesday that as soon as the merger closes, as expected in the first half of 2012 2013, the combined carrier will have dual-mode devices supporting T-Mo’s HSPA network and Metro’s LTE network ready to go. One of those devices might just be the iPhone 5.

Of course, T-Mobile and MetroPCS aren’t saying any of this out loud. It’s best not to test the Apple gods, and there’s certainly no guarantee that the companies will be able to strike an immediate distribution deal with Cupertino. But T-Mobile is already servicing more than a million iPhones on its 2G network and will ramp up its efforts to lure in even more unlocked iPhone owners as soon as it can fully support the device’s 3G capabilities.

T-Mobile may have to continue that bring-your-own-iPhone strategy for another year, but if all goes according to plan, by next spring it will have a fully Apple-compatible network in some of the country’s biggest markets, including New York City, San Francisco, Philadelphia, Las Vegas, Dallas and Boston. There are still a lot of obstacles T-Mobile and MetroPCS need to overcome to make this merger work, but at least the iPhone won’t be one of them.