Some celiac forums are claiming since they can eat it and it doesn't make them sick, it must be gluten free. Be careful of what you read, and find the source.
Personally regardless of the dedicated friers, Mcdonalds still does not claim the fries are gluten free, why? Cause the average fast food worker isn't really all that careful of cross contamination - they are getting paid minimum wage, which is honorable that they have a job, but commonly, they aren't that concerned with handling buns then fries. they aren't working in an environment that is allergy friendly.
Just keep that in mind when you shop for a quick break for food.