Promotion Dispute in Govt. Job

Dear Sir I was selected as Junior Engineer (JE) in state electricity board (HPSEB Ltd.) through HP Subordinate Services Selection Board , Himachal Pradesh in the year of 2009. I am holding B.Tech Degree, before joining my job. Now, I am in the seniority list for Promotion of Assistant Engineer. But recently, some of my Co- Junior Engineers, who were recruited with me and are very low in the seniority list to me, have been promoted before my promotion. The promoted JEs were Diploma holder (minimum qualification required for the post of JE) at the time of recruitment and, completed their degrees during job. Actually their are two promotion categories in HPSEB Ltd.,- 1) the JE who posses degrees before their recruitment in the job (my category) & 2) the JE who posses degrees during their recruitment in the job (category the promoted JEs posses). Now, i will be promoted after them and will be junior to them. Is it justified? I should go for a trial or not? what is the success rate, if i go for a trial? Regards Vicky