From what I understand they are on the other tribe and a part of the tribe until the merge which is EP7 I think. Thats how Sherea goes EP6 -- shes on Fei Long now and they lose IC and boot her.
Back to the switch~~remember Survivor Africa? Aaron gets "Silas-ed"
THE SWITCH: SILAS VOTED OUT
November 8, 2001
On Night 15, Silas Gaither, the 23-year-old bartender from Germantown, Tennessee, was voted out of the Boran tribe. Silas, leader of the young Samburu alliance, was thrown a curve ball when the unpredictable nature of SURVIVOR revealed itself. Each tribe was asked to select three of its "best" members, "best" meaning whatever they might interpret that to mean. When the three chosen members from each tribe showed up at a neutral location, they were informed that they were now members of the other tribe. Silas became a member of the Boran tribe, which intentionally threw the Immunity Challenge in order to vote him out. Leaving the Tribal Council, Silas looked back at his time in Africa, saying, "The twist in the game was amazing. I kind of had my cards lined up the way I wanted them to get through the merge. I couldn't recover from it. I was a threat to Ethan and the rest of the group. I planned on winning the whole thing.
http://www.cbs.com/primetime/survivor3/show/episode05/story.shtml