I know that the team at the Department of Finance did due diligence to determine the commercial viability of the project and were satisfied that it was commercially viable. Once the Government of Canada has secured ownership of the assets, that will be the time to determine the cost of construction and, of course, as a publicly controlled entity, in time, all of these expenditures will be made available to the public.
On June 20th, 2018. See this statement in context.