I was on vacation in Flavigny, an incredibly beautiful small village in Burgundy. I wanted my green beans straight from the garden behind the restaurant without butter and asked to use olive oil instead. The waiter was like "Why!?". It took me five minutes to convince him, he was absolutely unsympathetic and I think I had to pay extra. :)
Honestly, there is a bit of a pride fight in France between the butter cuisines at the North of the Loire river and the olive cuisines at the South of the Loire. So it might not be that much against the idea of make the dish vegan.
Still that useless, stupid pride. I cook burgeondy dishes with olive oil whenever I feel like it and it is still very good. Not quite the same taste but delicious nevertheless.