In order to impart a national character to student body, government has asked six colleges to take students through AIEEE, the national level exam. The colleges will start admitting a minimum of 50% (100%, if they prefer) of students through AIEEE from next year. Once a college becomes an IIT, it will switch over to IIT-JEE for 100% of the intake. Thus AIEEE is just a stop-gap exam till a college is converted into an IIT.
Any college that can not be converted into an IIT will be designated as INI. Then it will continue admitting students through AIEEE at the same original (50% to 100%) quota. The non-IITs (IT-BHU and Indian School of Mines) will continue taking students through IIT-JEE, irrespective whether they become IITs or not.
It is the govt. decision to grant admission through AIEEE before a college becomes an IIT and through IIT-JEE after it becomes an IIT.