Wait a minute?  Where is that $400B coming from?  Oh institutional investors who do what?  Invest in the Canadian Economy.  So?  We have now shift $400B from private productive investments into public far less productive investments. While there is no doubt that governments must keep investing in infrastructure to keep the economy rolling, syphoning billion from private investments isn't always the way to do it.  
In fact, most of the planned investments are not productive at all.
As an example, replacing efficient electricity generation with expensive and inefficient "green" electricity is actually counter productive as it is replacing an efficient system with an inefficient system.  
Another question is, how is setting up this bank any different than selling government bonds?  My guess is the goal of Morneau to simply to keep the deficit financing off the government books and hidden in the infrastructure bank.