It will probably start around June 25th, when the new Sims 3 Island Paradise comes out.
I'm planning to run a resort in the new EP. So maybe when Sims enter my resort, I can choose them to make it seem like a surprise enrollment for The Sims 3 Big Brother.
Also, when I choose 13 Sims, they're not all living in a house. Each Sim will have a photo taken and I will post the cast in the group! ^_^