I have been trying to get rid of Nuts in Costco bakeries. Years ago (10yrs) they never had "may contain". Now all their products have a may contain label.
Every time I go to Costco, which is at least 5 times a month, I fill in a comments card stating that they should make their bakery nut free. (I never sign my name, so they might think their is more than one person complaining).
If everyone who goes to Costco throughout the city, would fill out the comments card, maybe they might do something about it.