Depends how you qualify "reliable". If the investigation team are qualified, do exhaustive research, compare multiple items, study fact rather than ficion, and meticulously document their findings before making an objective decision, yes, they are reliable.
If a business or some independent entity is going to commission a consumer report, then I´d expect nothing less than experts doing the investigation.
As for companies "paying them off" ; I seriously doubt that is the case. They would, after all, be opening themselves up to criminal charges of fraud. They may well pressure investigation teams to produce a favourable report ( that´s lobbying and it happens everywhere) but if the team wants a truly objective result, they will take no notice.