In a warren of offices at a former bank building near Madison Square Garden, dozens of journalists are at work on gleaming new electronic equipment, ready to turn their test runs of Al-Jazeera America into the real thing. The Qatar-based news organization will finally establish a firm foothold on American television Tuesday after a decade of trying. At 3 p.m. EDT, Al Gore's former Current TV will turn out the lights in more than 45 million TV homes, replaced by the new U.S. affiliate of Al-Jazeera. In Houston, the network will launch on 4DTV (Channel W5261), AT&T U-verse (Channel 189),...