One of the local asphalt paving companies just bought a fleet of new trucks, and all of them have the same make/model CB antenna mounted in the same place on the trucks (Wilson 5000 CB antenna - trucker version). No idea what channel or frequency they use though, but since their trucks have no other antennas I think its safe to say they use CB for business purposes. I've heard other companies using out-of-band frequencies, but its possible they were just truckers.
Hopefully I'll be able to get a look inside one of their trucks at some point and see which radios they're using.
I know its not a business per se, but a government agency, but the Virginia Department of Transportation Safety Service Patrol trucks (along with some of their command/emergency response trucks) all have various CB antennas on them in addition to the hodgepodge of other antennas (their primary radio system is 45/47 MHz VHF low band, they also use the statewide Project 25 digital trunking system that operates in the 150-162 MHz VHF high band, some divisions lease channels on UHF trunking systems, and others still have 700MHz/800MHz antennas on them as well, probably for vehicle repeaters).
Given the numerous other communications systems at their disposal, chances are the CB equipment is installed to allow them to talk to construction contractors and/or regular old truckers. Seems like CB is the de facto standard communications system for road construction contractors, at least around here.
I also remember a local yard (located about 4-5 miles away from my location) that uses CB channel 31 to talk to the trucks loading and unloading in their area. A few years ago there was heavy road construction downtown and the dump truck drivers were using CB channel 35 to talk to each other.
I have also heard local dump trucks talking on 25.835 MHz AM / 25835 kHz AM - which is CB channel 19 "down three bands" (likely that the truckers are using Connex 3300 or Superstar-series radios with A-B-C-D-E-F band switches, the regular CB band being band D, they simply flipped the band switch down to A and kept talking while staying on channel 19. They were talking about loading and unloading things and were certainly very close to each other.
Since the place I live is the intersection of two major Interstate highways and several important US highways, the real CB channel 19, 27.185 MHz, is often extremely congested. There's one local CBer who has several amplifiers and an Antron-99 located on the roof of a several-story tall apartment block and he often strays from his "home" channel 22 and drops down to 19 to harass truckers. Several hundred watts and a well-placed antenna high above the ground means the CB operator in question can own channel 19 if he wants to (at least until the other guys who hang out on his home channel realize he's dropped down from 27.225 MHz to 27.185 MHz