No mcet exam is for its own college for these colleges you have to fill their respective for forms for bits pilani there is bitsat , for vit there is bites and for arm they do it through SRM jee.

Bitsat form is not out yet but you can fill the forms for srm jee and viteee.  It has been quite a while since their forms were out . The form filling date is likely to close soon . It would be closed by 29 th of feb . It may happen they consider your 4ank during counselling ,and it may provide you an extra edge but you have to fill their forms to be considered and appear in their exams

All the best : )