They will see first the position falling in which grade of Pay scale then they will see your current pay scale and inform you tentative pay as per their pay scale for this position and with some promises that in year or two you will be upgraded or elevated or pending pay revision your salary can be increase in due course of time.
This is what I experienced as Personnel Manager in PSU while we used to interview candidates. But I am not sure what is your situation and what is promised to you during interview. Mostly all PSU jobs are advertised with their pay scales for advertise jobs.
If not its unusual case.
2nd September 2009 From Saudi Arabia