I happened to notice this quite accidentally as the private cab was parked outside for a brief moment.
It both surprised me and, at the same time, looked like something totally reasonable. After all, if you're paying for a car to bring you somewhere comfortably, why not demand an internet connection on the go?
Funny fact: when I had just arrived in London, I thought that Addison Lee were a brand of public ashtrays in The City O:-)
Explanation for non-Londoners: there was a huge amount of public-service ashtrays near the doors of almost every office building, with an Addison Lee sticker, who were... the ashtrays sponsors!