Those parties are not the ones who conduct the impact assessment. They're the ones who provide input into it. The impact assessment itself would be overseen and conducted by independent experts. An academic setting is one place to look. Trade unions, industry associations, Colombian government representatives, and others would provide input into the assessment. The information would then be analyzed, gathered, and put together, after which conclusions and recommendations would be formulated by the independent experts.
On November 26th, 2009. See this statement in context.