In HR language, many at times the jargons that we use do lead to confusion and contravention.
Answer your question, PE cant take the "interview" of CL for sure as its proving some relationship between PE and EE in the selection of CL which shouldn't be.
However, I would suggest you change the terminology as "assessment of the skills of CL", which would be possible by the PE before deploying into the work. The assessment can be done thru interaction, questionnaire or any other appropriate modes, but the presence of Contractor / Contract Supervisor during is must.
You may ask if any further clarifications on this.
I think it is better you employ direct workers/ employees rather than depending upon contract workers for such activities by interaction, questionnaires etc.
It is true that many multi crore business houses are working in India which do not follow the labour rules and most of these companies engage contract labour without complying the CLRA Act. they are doing so not by ignorance but as a matter of their right on the faith that they will get the protection from the ruling political parties. But if something happens and the media interferes the top management will wash their hands just by saying that "we have an HR person whose major role is to ensure compliance and it is unfortunate that he has not done his job properly!". This is history of any dispute which has been exposed.
Therefore, don't think it as HR jargon but an HR truth.