This happened earlier today in the Maison. I was at battle 50 in Super Singles, fighting the Chatelaine. I lead Mawile, she leads Thundurus. Thundy gets a Wild Charge off as I Mega Evolve and OHKO with Rock Slide. No big deal.
Then Landorus comes out. I know from a previous misadventure in XY that it's Scarfed. No big deal. Anyway, I switch out to Latios as it goes for Earth Power, which obviously does nothing. I know that AI trainers are coded to switch if they can't do anything, so I press Calm Mind to get the free +1/+1. But it stays in. This Landorus stays in and keeps spamming Earth Power, allowing me to set up 6 Calm Minds. I then obliterate Lando with Surf, and Tornadus falls to a Psyshock shortly after.
So thanks, Chatelaine-who's-intended-to-be-a-difficult-boss! Thanks for letting me effortlessly sweep you!