What you say is correct - a WBS is required as that would reduce...

What you say is correct - a WBS is required as that would reduce the variance. However, it would be difficult at this stage as many technical aspects of the plant are yet to be decided or declared. This is how we are are all going to determine the cost of production and determine our profits or losses.
It all comes down to processing cost - the price and volumes involved i assume will be modeled to determine breakeven points based on the 2 main variables in the commodities involved.
Obviously we do not have enough info to determine this yet and rely on the prospectus. I can understand why a WBS is not done yet from an investor perspective however it does not mean it hasn't been done unofficially. It just has not been released is my thought as these would require significant assumptions and commercially sensitive data before any acquisition has been completed or business commenced.