The precise value-added role of having an independent, arm's-length entity is that a public sponsor brings forward a project. Then, really, it's up to the bank to determine with that sponsor whether or not there is an appropriate investor base for that particular project. That really is a market-determining function of whether or not a project is bankable, and that provides the feedback mechanism to the sponsor of that project as to whether they want to continue under the infrastructure bank model.
On May 30th, 2017. See this statement in context.