The crap they show in the back of NYC taxis does seem to fit the bill (short 2-3 min videos, changes fairly regularly, though heavily mixed with advertisements). It is crap, but I imagine once there are driverless cars, the format will gather interest from more creative sources.
Why use it for creative purposes when you can use it to show ads? Talk about a captive audience. I'm betting that Google is going so big into driverless cars so they can show you ads on the windshield once it's proven + accepted as safer than human drivers. It might take 20 years, but they're opening up a new advertising channel.
