I don't believe there an automatic "UnFillet" (except CTRL Z :)
but you can maybe make something like this

Line Web : http://moi3d.com/forum/index.php?webtag=MOI&msg=3666.1

Copy vertically your curve
Call LineWeb
Connect by line (any number you want) here 10
Select the vertical lines created - only little problem you must select these vertical lines in order horlogic or unhorlogic
(no problem if your first curve was drawn in order so a rectangular selection from Right to Left will work)
Connect lines "Closed" enable (3 as number) :
You have your curves with angles points! Maybe with a little deviation but... ;)