I can't say anything about Montreal specifically, but when I was an LPR in the UK trying to get a B1/B2 at the London embassy, my IO called up someone else to talk to me for a few seconds and he spoke my native language fluently with an easily identifiable American accent. I inquired about it after he was satisfied with my answer, he smiled and said there where translators for every language.
It may have been because the embassy in London was a large one but who knows. If your parents speak a language that has a large enough presence in the country, they may accommodate them.