If you mean to just Import the Flash Game into Unity, or directly "OPEN' a flash game with Unity, then I would say no. You will need to re-write the flash game in unity.
Apparently yes, but not by any official means. I know that the developer "Lachhh" from Berserk Studios wrote a tool for their game "Just Shapes and Beats" that converts Flash objects into Unity objects, but I don't think he's published this tool for public use.
Thought I would share this. We chanced upon this great blog post where SFB Games talked about how they converted Tangle Tower's art and animation from Flash into Unity. It was a great read and I thought this may be of some interest to you guys. Quoting from the article, SFB Games has been "using Flash to make games for 18 years now, with no signs of stopping. These days though, we only use it for art/animation, not the full game!"