Could The Edge Vent be safely used for intake at the transition where a pitched roof meets a flat roof?

No. The Edge Vent should not be used for this application where a sloped roof meets a flat roof.

Air Vent does not recommend the use of The Edge Vent for this application where a sloped roof meets a flat roof. Not only is there an increased possibility for infiltration, the vent would be covered most of the winter with snow.