Perhaps in response to T-Mobile USA CEO John Legere’s New Year’s resolutions -- which included “giving AT&T a break . . . or not,” AT&T is giving the fourth-largest wireless carrier’s subscribers a new reason to migrate to its network Relevant Products/Services.

As of now, AT&T is officially offering T-Mobile customers the opportunity to “upgrade their mobile Relevant Products/Services lifestyle” with value of up to $450 per line when they switch to AT&T and trade in an eligible smartphone.

AT&T is ticking off reasons why T-Mobile customers should take the company up on its offer. In addition to the $450 per line, AT&T pointed to its “larger and more reliable 4G LTE network.” The company also promised switchers a superior smartphone lineup and award-winning customer Relevant Products/Services service.

Throwing Barbs and Gauntlets

For reaction and analysis of AT&T’s big marketing Relevant Products/Services move, we turned to Jeff Kagan, an independent technology analyst. He told us AT&T has decided to fight T-Mobile in a very creative and likely effective way.

“We have been hearing T-Mobile throwing barbs about AT&T for the last several quarters,” Kagan said. “So far it doesn't look like this has hurt, but AT&T has decided to stop taking the punches in the gut and start punching back at T-Mobile.”

As Kagan sees it, this raises another question: T-Mobile has been winning customers in the last two quarters but we don't know whether those customers are satisfied or not. AT&T’s promotion, he suggested, could let us know just how satisfied T-Mobile customers really are -- or at least offer a hint.

“Will customers who switched to T-Mobile stay there, or will they leave because of quality and speed? We aren't looking at a 100 percent move one way or the other,” Kagan said. “Some customers will stay with T-Mobile and others will leave. It will be interesting to see what the numbers are and what happens next. This is becoming a real marketing battle. The saga continues.”

How to Get the $450

Here are the details of the AT&T deal: Under the limited-time offer, T-Mobile customers who switch to AT&T can trade-in their current smartphones for a promotion card of up to $250, which can be used toward AT&T products and services.

Trade-in values will vary based on make, model and age of the smartphone, but AT&T said many of the latest and most popular smartphones will qualify for a value of $250. T-Mobile customers can receive an additional $200 credit per line when they transfer their wireless service to AT&T and choose an AT&T Next plan, buy a device at full retail price or activate a device they currently own.

AT&T’s new Mobile Share Value plans offer data Relevant Products/Services and unlimited talk and text starting as low as $45 per month with no annual contract. AT&T Next offers customers the chance to upgrade to a new smartphone every year for zero down.