The "on the brink" manual states that outbreaks flare-out (bioterrorist challenge). But how about the mutation challenge? Does the purple cubes' outbreak happen like the normal ones?
Yes. See page 4, Mutation challenges, Infections: "resolve any outbreaks *normally*". [emphasis added]
Also see the note on page 6, Bio-Terrorist, Purple 'Flare-Out' Outbreaks: "This applies to the Bio-Terrorist challenge only, not the Mutation challenge."