The extra cost of the first twenty buses is being covered by a federal grant, although it's not clear at this point how the other forty-nine buses will be paid for. The buses are being built by California-based Gillig and they use the GM Two-Mode hybrid system with a nickel metal hydride battery. The early experience of hybrid buses in Seattle proved to be disappointing with hybrid buses getting lower mileage than conventional buses. A later study conducted by the National Renewable Energy Laboratory compared the hybrid and conventional buses over the same routes and duty cycles for a six-month period and found the hybrids to have a 27 percentage advantage.
[Source: MetroMode via YpsiDixit]