Basically, the criteria had to do with technical skills, financial strength, construction expertise and so on. Initially, there were six groups. The objective of this exercise was to reduce the number to three because, in the next step—the request for proposals that is being implemented right now—these groups had to invest a substantial amount of money to bring the proposals to the level of sophistication required for their submission.
On March 10th, 2015. See this statement in context.