Hi Cloud Clutter,
The restriction on the flap setting is brought about by a requirement to maintain the flap setting at the time of a pitch (elevator) jam not due to the icing conditions. The icing requirement is not necessarily brought about by the actual presence of ice. Any time visible moisture is present on the ground with a temp of 10 deg or less, the icing systems are on and the additives are made to the speeds.
And for another post, of course Eastern still operate the 100 series Dash. And what a great machine they are.