hello,

after clearing diploma you can certainly join btech, but join in mba is not possible, the eligibility criteria for mba is you need to have graduation degree in any discipline from a recognized university.

how there is many psus like power grid, npcil, ntpc recruits candidate for apprenticeship  program of 1 year, which is really good for your technical career. also you may search in state electricity companies.

also you can apply for rail, ssc diploma engineering exam.