I received the answer of this query from ICAS today.
For university education completed in Pakistan, ICAS will prepare an assessment of the study provided that the university was formally recognized by the Higher Education Commission (HEC) at the time of admission.
Please review the specific documentation requirements by country at
http://www.icascanada.ca/new/immigration-to-canada.aspx/documents.aspx. You will note that there are specific documentation requirements for education completed in Pakistan.
For university education completed in Pakistan, we require HEC-attested photocopies of both the graduation diploma / degree certificate
and marks certificates submitted to ICAS in an envelope that has been signed and sealed by the
Islamabad office of the HEC (Higher Education Commission)
at the time of attestation. ICAS will not accept documents which have been previously attested and packaged by the HEC at a later date.
The HEC must attest both your original documents and a set of photocopies. The HEC will return the attested photocopies documents in a stamped, sealed envelope. You must then submit this envelope to ICAS unopened. For information about degree attestation, please visit
www.hec.gov.pk and
http://das.hec.gov.pk/. The HEC is not required to complete the Official Records Request Form.
Even if your documents have been previously attested, you must follow the above procedure to obtain the attested copies in a sealed HEC envelope. You do not need to be physically present in Pakistan to request the service. It can be completed entirely by courier. Details are available on the HEC website.