PSUs looking for profile relevant to Master’s specialization are the ones which recruit mechanical engineers. Typical examples are Iocl R & D, ONGC’s PGET (Post graduate engineer trainee) and a few more.
However, you cannot expect a PSU to hire you after M.Tech if they are looking for a GET (Graduate engineer trainee) profile. In that case, fresh graduates are preferred.
If you want the GET profile of PSU, than it is only possible through the recruitment based on GATE score. You have to repeat GATE every year with flying colours to become eligible for the GET recruitment through GATE.