Been following this with some interest and I see the Boeing 737-800 FCOM allows it subject to 'regulatory approval', so your airline Ops Manual should say yeay or nay.
So many aeroplanes have piled in because of ice, and still do, that I find it strange how the rules change and if frost is now allowed on the upper wing surface.
- I'm not sure, but I suspect there was more than a small amount of thin frost in an approved area of the wings on most of the 'departed'? The 'no ice' rule is possibly just a (sensible) blanket restriction which can now be reviewed after satisfactory investigation/testing? Things do move on, and sometimes for the better.
The Boeing 'limitations' on it are quite specific.