Thanks for all the suggestions. I will need to check Spline Fit plugin and Curvizard. Sorry for not being 100% clear with my explanation, I agree that I should have had picture in the beginning to explain the matter.
Here is what I am looking for, see below. Basically I would like to modify my contours so that I could add more line segments into the straight parts. This would be essential when creating terrain mesh.
Actually, I did some testing with Curvizard and I didn't find a way to add segments to straight parts without affecting the round parts. When using poly divider function I get more segments in straight parts part but I lose the multiple segment in round parts, and therefore I lose the original form of the contour.
http://i.imgur.com/apKLBc7.png