Hallo,
By the WPS Qualification and the Welder Qualification (ASME IX), the welding of the test pieces and the testing of the test pieces (N.D.T. and D.T)shall be verified (witnessed) by an examiner or examining body ?
Per ASME IX, witnes and certification of welding procedure qualification and welder qualification is the resposibility of the manufacturer or contractor (employer of the welder) - not a third party organization.
Subcontracting testing and NDT is indeed permitted and does not need witnessing, provided you take responsibility under certification of the PQR per ASME Section IX guidelines.
I do not know if it applies in all jurisdictions but in Ontario the results and bent plates must be reviewed by the AI before the procedure can be submitted for registration.