I will answer that indirectly. The NEB does not do separate studies on those kinds of issues. It does an overall assessment of the supply and demand market in Canada. However, if a phenomenon like the one you described were to occur, the cause would be what is known as a market imperfection in economic terms, in other words, inadequate transportation between those producing the economic or energy commodity and those wanting to purchase it.
If you impose a constraint between the two, you are creating a market distortion and thus diminishing the result you would have gotten with economic efficiency in a competitive marketplace. I would say there is a social consensus that economically efficient markets are seen as being in the public interest of Canadians.