You're talking about the WTO market access conditions right now. The idea is that there would be special arrangements for products defined to be sensitive, and there would be some upper limit.
It depends who you're talking to. The various tariff lines would define the percentage in terms of covering off every supply-managed product. I think it's a bit over 5% that they would cover off, so they wouldn't be entirely immune. However, they are very ingenious at redefining things and putting things into other categories. Cheese compositional standards come to mind.
Even if there was a pressure there, there are a lot of smart people around who are going to be very ingenious in redefining exactly what fits where in a tariff line.