Thanks for the question!
Yes, surely you can do a govt. job and there are no barriers to the promotions too. According to the treaty signed between India and Nepal in 1950 during the Rana rule in Nepal. According to the treaty, Nepalese can work, travel, own property and do any other activity freely in India.
Follow this thread for more clarity - http://www.lawyersclubindia.com/forum/Do-Nepalese-Need-a-workpermit-to-work-in-India-27600.asp