For Folks wanting an episode on a Bus...
https://youtu.be/3H02J61Ma5A
I think that's a about as close as you will get for now, Dr Who On The Buses :-)
Wow, ok so a year after you posted this and I just finished watching season 9 final episode and guess what?!?
It ends with them doing a On The Buses skit!!
https://www.imdb.com/title/tt30248665/?ref_=ttep_ep6