Business Green: Earlier this month, AT&T made a major announcement: It will invest more than a half-billion dollars over the next decade to purchase more than 15,000 alternative-fueled vehicles, 8,000 vans powered by compressed natural gas, and another 7,100 hybrid passenger cars. The telecommunications giant estimates that the new vehicles will save 49 million gallons of gasoline and reduce carbon emissions by 211,000 metric tons over the 10-year deployment period – equivalent to removing the …