Select some edges..
The script will create a curve from those edges.

Select Multiple Edge 'Islands'
And you get multiple curves

Select Multiple Overlapping Edge Islands
And the script tries to interpret what you mean. Here you get three discrete curves.

Select Overlapping 'Closed' Edge Groups
And you get separate closed curves..

Select Overlapping 'Closed' Edge Groups
And you get separate closed curves..

Select Overlapping 'Closed' Edge Groups and single edge islands
And you get separate curves..the open ones open and the closed ones closed.

Works Well with JJ_curvealign.py
Letting you create curves and then plant a poly directly on the curve. For more info on jj_curvealign click here.

Potential Problems
Although this example works you can get a few problems with overlapping edge selections that are hard to split up into edge islands or discrete closed edge selections. I'm surprised this works!