MetroPCS turned up wireless service in Los Angeles today, marking its entrance in the country’s second-largest market and a key stepping stone in its plans to expand to the Northeast.

The carrier’s initial launch uses Alcatel-Lucent CDMA gear and will cover 11 million people in the L.A. metropolitan area, one of the densest regions in the U.S. as well of one of the most contested areas among the nationwide providers. But Metro president and Chief Operating Officer Tom Keys said Metro is committed to being a major competitive force in the area, offering unlimited calling plans for as low as $30 a month and building a sizable local presence with 20 company-owned stores in the city as well as third-party distributors. In many of its markets, Metro has achieved 5% penetration in the first 12 months of operation, Keys pointed out, which, if achieved in L.A., could add sizably to its subscriber base of 3.5 million.

In contrast to the national carriers’ minute plans, MetroPCS offers all-you-can-eat service plans in its local markets, much like fellow regional provider Leap Wireless, a company Metro is actively courting for a merger. Unlike Leap and many other smaller carriers, though, Metro isn’t focusing on small, mid-sized or rural markets. Instead it’s going after the big metropolitan regions where competition among Tier 1 operators is fiercest. Metro has service in San Francisco, Dallas, Miami, Orlando, Detroit and Atlanta as well as a few smaller cities, but its ambitions lie in the largest cities in the U.S.: Los Angeles and New York.

Metro received licenses for both markets in the last two FCC auctions for PCS and Advanced Wireless Services spectrum. The L.A. launch, however, came two and a half years after it first won the licenses, a fact that Leap actively criticized in its rejection letter to Metro’s merger proposal. Metro offered Leap a stock swap worth $5.5 billion that would have exchanged 2.7 shares of Metro stock for every share of Leap stock but would have left Metro shareholders in firm control of the company. Leap soundly rejected the deal, not only claiming that Metro was undervaluing Leap’s business but attacking Metro’s own business execution. Leap claimed Metro was well behind in its L.A. launch and would have the same difficulties turning up New York.

Keys said the accusation was completely unfounded and probably used to gain leverage in merger negotiations. “We’re on time,” Keys said. “We told the street we’d be launched in the third quarter, so we’re in line with our guidance.” As for Leap’s public airing of its criticisms, Keys said Metro plans to take the high ground. “It’s out there—we’ll see where it takes us,” he said.

With L.A. live, Metro is now focusing on the Northeast, where it owns three major licenses in New York, Boston and Philadelphia, all of which will be launched in late 2008 or early 2009. The L.A. launch will be a critical lesson for Metro in dealing with sheer scale, Keys said.

“With every market we launch, we get better, we get more efficient,” he said “We’ll bring that with us to Northeast at the end of ‘08, beginning of ‘09. Let me put it this way: L.A. helps New York get better.”