You will not be permanently banned for boosting, but they have been resetting / temp. banning people who got reported, and had other persons IP's connected to them. So if you logged other accounts, and did not do anything to hide it and played arena, I would not be suprised if you got your titles removed.
In S8 when I was doing a boost to rank1 on Cataclysm bg, Skoez and his team of shitters reported me (obviously after being cocky about it, trying to snipe us and being put back in the dumpster after failing). The entire 5v5 team was reset on the account I was playing on, and my main got banned for 48 hours.