Hi Tete,
I had a similar situation yesterday, but she (driver) wasn't driving a bus and it wasn't a steep hill. But IMO it constituted thoughtless if not dangerous driving and since her window was open I sidled round to tell her.
I knew she'd heard me shout "oi!!!!" because she refused to look, staring steadfastly ahead [why do they do that??]
Then, when I forced the issue her opening lines was "I used to cycle so I know".
"Know what? That was dangerous driving back there."
"No it wasn't."
"Yes it was. You pulled in to the left before you'd safely overtaken both me and my partner. You didn't know where we were and when I shouted I saw you look up to the mirror. Please give cyclists room."
"I used to be a cyclist."
"You certainly don't drive like one, that was dangerous."
"No it wasn't. I used to cycle."
"You should think a bit more about that. If I thought your driving was okay I wouldn't be here talking with you would I?"
[steadfastly looks ahead, drives off when lights change].