I can't speak for the CNSC, as they would make that decision. From a reactor safety point of view, you can operate a reactor with a small positive power coefficient. It's not the desirable method, but it can be done, and you can do it safely. What you have to do is slow down the way in which you move the rods so that you bring more control, or a very high level of control, into the system.
So it is possible to operate the reactor with a small positive coefficient as long as you can predict exactly, as you said, in your calculations that this is how it will work, so that you will know exactly what's going on.