That is an excellent point, and in my haste I forgot to consider that aspect. After reading your post though I still feel it a non issue, like you do.
Fact: CCME has the PRC blessing as the sole advertiser on inter-city buses.
Fact: The companies that advertise now, like ALL companies, test the ROI on their advertising expenditures. Many large names are currently advertising with CCME. If CCME were a fraud, these clients would realize that there was NO impact from these ads, check in to it, find no buses running their ads and cancel the contracts. This has not happened. This isn't Coke's first rodeo.
Fact: If you want to advertise on inter-city buses there are no options. Same with the airport bus routes they have. A large company like Coke does not sit there and think "If our potential customers see an ad on a CCME screen they will know that there are fraud allegations against CCME and equate us to them." Nope. Coke thinks "We need to get a picture of a damn Coke bottle in front of these hot, tired thirsty people - what are our options? Oh, CCME is it? Then CCME it is."
That's my take on it anyhow.