I found video of the bus fire. The bus was called 'The Yellow Rose of Texas' and belonged to Veterans for Peace member, Jim Goodnow. He used it to transport many Iraq Veterans Against the War members to various events. You can keep up to date on their situation and make a donation at the link above.
Jim saw, in retrospect, some suspicious activity outside the bus, and about 20 minutes later, the entire engine compartment, and back of the bus was engulfed in flames.