First of All they don't Short list people from computer Science or IT Engineering background. Mind it -- I am saying people with CS/IT as their Engineering major.
In the interview emphasis is on what you have done in engineering and they are going to check you on engineering concepts as well. Again Mind it -- they are here to recruit managers from MBA institutes and probably many of you may have 3-4 years of work experience and would have forgot all the concepts.
Last but not the least -- Go through the power sector in detail. (especially Indian scenario)