Exclusive Responsibility vs. Exclusive Work

It seems that the big hang-up in the current negotiations between AGSEM (the TA union at McGill) and the McGill administration is the question of whether or not the work assigned to the TAs on their workload forms is exclusively theirs or not. If it is exclusively theirs, then no one else can do that work should they go on strike. If it is not, then the course instructor can step in and do whatever needs to be done during a work stoppage.

That this would be a deal-breaker for the union makes perfect sense to me. If the union were to agree that TAs had no exclusive function, then striking seems to go out the window. Or, rather, striking would cease to be a confrontation between the TAs and the administration and would become instead a confrontation between TAs and their supervising faculty. If my TA goes on strike that means I have to do a bunch of extra work. No union wants to to get its members into that sort of bind. The line of confrontation must be between workers and management, not between two groups of workers.

Why the University should be equally adamant about this issue is a bit harder for me to see (unless one wants to attribute purely cynical motives to the administration, and that is never very satisfying). Here is the rationale the Provost has put up on the website:

Since the start of this unfortunate strike, professors have sent me a consistent message on this matter: do not compromise on this principle. Let me quote you one such particularly eloquent message:

The idea of exclusivity is absolutely unacceptable, and the university's proposed revisions to the workload form are clearly needed. The more AGSEM insists that it does not view the exclusivity question as closed, the more important it is that it be settled somehow, and the workload form is a good way to do it. Exclusivity is not simply a matter of TAs' working conditions; it is a matter of faculty working conditions, too. Exclusivity would mean a serious impairment of professors' pedagogical autonomy, and a serious infringement of our ability to meet our responsibilities as educators.

A colleague I respect said something very similar to me just yesterday. Frankly, I just don't get it. I don't see how my autonomy or responsibility as an educator is affected one iota by me being unable to take over my TAs conferences or grading in the case of a strike. I would still make the syllabus and delegate tasks to the TA. I would still bear final responsibility for checking and rectifying grades, for determining the form and content of the course, for setting the standards by which student work is to be evaluated. In short, I would still have ultimate responsibility for the course. But that doesn't mean I should be able (or required) to step in and do everything in the case of a strike. The Provost's position just seems like a non-sequitur to me.

There are other employment situations in which a similar distinction must be drawn between work and responsibility. Nurses, for example, have work that is their own, even though doctors have ultimate responsibility for patient care. And, in fact, the University seemed to recognize such a distinction early on during this strike: no one asked professors to run conferences the last week of classes.

Can any one explain the University's position to me in small words that I might understand?