The consultant company was doing work for Rio Tinto on the Project. Payments made to them for their work should not be called bribery, since it was for actual work on the project, according to all stories relating to this subject.
A Consultant is a Contractor that should be paid for the work they do.
If all consultant work is called Bribery by Rio Tinto, all Consultants and Contractors should quit working for Rio Tinto. Let Rio Tinto hire their own company personnel to do any work that needs done.

Contractors should avoid Rio Tinto with a passion. There are other companies out there that need contract work done. They would welcome consultants to help them with what they are doing.