A handout photo released by T-Mobile, shows T-Mobile CMO Mike Sievert having his hands full with complicated competitor rate plans at a news conference in New York, 26 March, 2013. (GARY HE/INSIDER IMAGES/HANDOUT/EPA)

Whether it was pent-up demand for the iPhone or an endorsement of its “uncarrier” approach to wireless plans, T-Mobile must be doing something right. The nation’s fourth-largest carrier reported Thursday that in the past three months its subscriber rolls have swelled by 1.1 million new customers.

That accounts for the largest boost T-Mobile’s seen for net additions in four years, and a marked improvement from the 200,000 subscribers the company lost in the same period last year. There are caveats to that number — only 685,000 of the customers T-Mobile added come from the more-profitable postpaid customers, a.k.a those with contracts. But, as InformationWeek noted, that’s still more than the 550,000 postpaid customers AT&T added in the same period, or the 1 million subscribers that Sprint lost across its platform in the second quarter.

Of course, T-Mobile has had a very busy year so far. Not only did it finally plug the biggest hole in its product lineup with the iPhone 5 in April, it also introduced new plans that explicitly separate out the cost of users’ devices and data plans and allow customers to update their phones more frequently. Plus, T-Mobile also sewed up a merger deal with MetroPCS, which in turn has built out its nationwide presence by adding 15 markets across the country.

All that comes against a backdrop of the carrier’s continued work to stem subscriber losses over the past year and build out its 4G network in order to more effectively compete with its larger rivals.

This quarter’s earnings seem to signal that the carrier is at least headed in the right direction for a comeback. The real question, of course, is whether T-Mobile can continue to ride this momentum and add customers beyond the initial pushes for its new plans. But in a company release, chief executive John Legere sounded predictably upbeat about T-Mobile’s prospects for a turnaround.

“We are just beginning and we will continue to apply this innovative thinking to the Un-carrier offers we create and to the internal operations of our company, which taken together are driving significant shareholder value creation,” he said.