Yes, Joseph, if “surely” is enough to permit imported lemon juice, when we have no information at all about what sort of keilim were used to cut and squeeze the lemons, or what was kept in the barrels before the lemon juice, etc., then kal vachomer that it’s enough here.
We rely on “surely” throughout halacha — we call it “chazaka”.
Of course if they did have separate scoops then the whole problem wouldn’t exist in the first place. So I assume they don’t, and I suggest that surely they rinse the scoop between flavors, so it should be OK.