Well, as per my information, NITB only trains Officials being sent to them through Government Organizations (Ministries mainly), you can see here:

http://www.nitb.gov.pk/frmdetails48c9.html

You are right in regard of NITB training being set by Estab Div for recruitment on said posts, so best would be to contact NITB:

National Information Technology Board
24-B, Street No.6, Sector H-9/1 Islamabad.
Email: info@nitb.gov.pk

Tel: 051-9257781, Fax: 051-9257724