OK, this fact sheet definitely says the time for travel from worksite A to worksite B must be paid. Some things are not clear though.
Ordinary commuting time from home to a fixed workplace is not paid. But travel time to a temporary work place may be paid. This seems to describe the situation when one is dispatched to client homes ad-hoc, as described here. But I'd like to see that in black and white.
Another likely complication is that the employeer may claim (spuriously) that the employees are 'indepentent contractors,' in an attempt to evade the usual wage and hour rules.
Fact sheet:
http://www.dol.gov/whd/regs/compliance/whdfs22.htm