I read about that; it was real effort to pick only the docile ones for the breeding programme, but it showed that it was possible.I once read an article about a Russian researcher who took to domesticate fox. If I remember correctly in about 20 generations the foxes were quite "doggy" and suitable to be pets. I don't think I have heard how it ended.
Did he not do it at a fox fur farm ?
I think the article I read was in the New Scientist ....maybe
Anyway, I found a bit about it on Wikipedia....silver fox, domesticated in Siberia.