Off hand, I don't completely recall, but I do remember it stating something along the lines of:
"declaring the use of a NFA item before entering the range"
What exactly that would mean, aside from saying I'm shooting a SBR/can, I can't say for certain.
I've seen the signs up recently at both Kennesaw and Powder Springs. Currently don't own any NFA items, although I do have plans for a SBR and can. As for collecting brass, I've never had any issues with it at either location.
Will agree though, it's a night and day difference between the two...