Lots of technology (Score 1)

You could have a computer detect when ever it sees a lense (Camera, not glases) and have it shine a laser into it. Depending on the size of the bus and how fool proof you want the system to be I'm sure for a typical limousine you could have an array of say 100 camera's around the top sides and floors and an other 100 lasers that could be aimed at lenses when required. It would not be fool proof (maybe 80%?), but I'm sure that for around 10-30M$CAD (Only 9-27M$USD) of hardware (off the rack cameras, motors, lasers and computers that you could pull in a trailer behind the limo) and custom software you could have a pretty effective solution.