About no objection certificate

When you applied for this JE post were you working in railways as ALP? Did you apply for the post through the department and you applied separately? Did you mention in the application that you are working in railway as ALP?
If you applied through the department that itself is a NOC and no separate NOC is required now.
If you are resigning from the post you are presently working and if you are getting the relieving certificate, then you don't need NOC.
But without resigning if you want to shift the job so that your service as ALP will also be counted in the department, you have to obtain NOC and then join the new job. You have to contact your immediate boss and explain to him and get the NOC. It will be always better.

When you are working in a department and want to apply in other department or some other position in the same department then it is always advisable to apply through proper channel. If you follow that practice yo will easily get a NOC and your resignation and discharge process will be simpler and convenient. We should not take the matter of NOC lightly. NOC does not only vouch for your earlier service but it automatically conveys a good conduct by you in your earlier job.

If you have not followed the NOC procedure in this case then I will suggest you to meet your present head of the department and talk to him about this lapse on your part. As you are moving from one department in the Railways to another department in Railways only then he will help you in getting released at the desired time. You have to take him in confidence and apologise for not adhering to the NOC procedure. Please remember you can not keep the present head of the department in dark about your plans to apply in other places and change your job. He has also to arrange a person in your place and he will like such information to be shared with him at the time of applying itself.