I thought this article was going to be about how he hid a Linksys WRT54GL on the actual buses to gather the real-time bus data himself! <:)
One could hide Raspberry Pi devices on the buses that are programmed to geolocate using Wi-Fi networks along the bus route and then opportunistically use any open Wi-Fi networks to upload their current position.
Connecting to Wi-Fi on the run is probably not feasible most of the time. DHCP is slow on most residential routers.
Maybe it could work by cheating (e.g. sending UDP packets to multiple common IPs of routers, like 192.168.{0,1,2,3}.1, without waiting for DHCP), but the auth frame exchange alone would probably take too much time.
One could hide Raspberry Pi devices on the buses that are programmed to geolocate using Wi-Fi networks along the bus route and then opportunistically use any open Wi-Fi networks to upload their current position.