Does the Hay System force an employer/union to use a pay line based on local pay scales they feel are normative?

Does the Hay System force an employer/union to use a pay line based on local pay scales they feel are normative or can the employer and union negotiate their own pay scale but still use the rest of the Hay software, ie. job description templates etc the information needed to decide where a job lands on the pay line

there are 2 different things:
being unionised or not..
next i have worked on hay point factor n salary surveys too.
Hay is not the only vendor of such services... there are other good vendors also avl like mercer/ towers n watson etc
for job description templates, i dont like Hay actually..
i find O-net as one of the finest resource.
i feel someone is simply gathering evidence n re-affirming a particular line of thought...