The issue is governance.  Liberals want a free hand to reward party loyalists, and to mine opportunities for back-door political funding via traditional Liberal Party contractual king-making.  
One need only look at Infrastructure Ontario for a living example of black-hole dynamics operating at the epicentre of the huge capital spending flows overseen by government.  The Liberal government appoints party loyalists who in turn employ corrupt operators like Vas Georgiou to do the government's dirty work without directly staining government ministers when the labyrinth of corrupt dealings is eventually exposed.
The Infrastructure Bank proposed by Morneau is the civilized world's version of the 10% kickback men who direct financial dealings in corrupt third world countries.  It is the governance set-up that tells us this is so.