If students select to go for the paper based exam i.e. T5 T6 or T7 then they can sit in these exams in June 2011, however, if students go for transitional papers i.e. TT5 TT6 and TT7 then basically he is sitting current F1 F3 and F2 respectively.
So, under transitional arrangements you can sit in CBE exams as and whenever they are scheduled by the institute until November 2011.
To understand more about CAT transitional arrangement papers check out What is CAT TT5 TT6 and TT7?