I believe that they can, but with extreme caution - and from what I recall, both should not be added to the tank on the same day.
Between the two, you can get some pretty serious bacterial blooms that will wreak havoc on your QT.
I've tried it - and consequently avoid it whenever possible.
~Bruce, who's very capable of being wrong - if Humblefish, Melypr1985 or 4FordFamily tell you any different ... listen to them, for Heaven's sake!