General Motors (GM) vehicles enabled with 4G LTE connections are set to hit the roads next year, as the automaker struck a new deal with AT&T.

AT&T and General Motors' OnStar service unit reached an agreement to bring millions of connected cars to the market. The 4G-equipped lineup will start with the 2015 fleet, which comes out in late 2014. According to GM, most Chevrolet, GMC, Buick and Cadillac vehicles will get wireless connections.

The move marks a major step forward for AT&T, as the carrier proved quite aggressive when it comes to the connected car business. The company believes it can eventually draw as much as one billion dollars in revenue from this endeavor.

The collaboration further breaks a long-standing affair between OnStar and AT&T archrival Verizon Wireless, which served as the traditional provider of older wireless services.

"The excitement is you're taking a car and turning it into a smartphone with four wheels," AT&T president of emerging services Glenn Laurie told CNET. "There's an opportunity to do amazing things with the car."

A fast wireless connection also adds a range of possible new services. Drivers can benefit from more Internet radio options, more accurate traffic data and other such advantages. OnStar, meanwhile, can take advantage of the 4G LTE connection to better track the condition of the car, checking to see whether it needs any maintenance. The vehicle could even serve as a 4G LTE hotspot for mobile devices such as smartphones and tablets.

"Through this built-in 4G LTE connection we have the opportunity to reinvent the mobile experience inside a vehicle," says Mary Chan, president of GM's global connected consumer unit. The automaker further said it would offer the necessary tools for developers to create apps to maximize the car's connection.

AT&T first started negotiating with General Motors a few months ago to replace Verizon as the wireless provider for GM vehicles. AT&T plans to cover 300 million people with its 4G LTE by the time the new cars roll out. A few GM connected vehicles will be on display this week at the Connected City section of the Mobile World Congress (MWC) trade show.