Now this isn't the first bus with Bitcoin on the side. Exchanges have been promoting their brands on buses in a number of cities, ... Hong Kong, London, etc.

But this bus has Bitcoin on it not because of some sponsor paying them for it. This bus has Bitcoin on it because that's what these bus operators do in Kenya. They need to differentiate themselves from the other buses, so they use murals and paint -- choosing whatever design they want to share.

Here's more on these buses (called "matatus"):

Nairobi's Matatus, pimped-up rides like no other https://www.youtube.com/watch?v=RJXjCp5U1xk