I looked at the dwg file, it should not be hard. First you need an ordered list of curves for each set of connected curves. I think you have to try creating PolyCurves (you will have 3) and then breaking them again into individual curves to get an ordered list of curves.

for each set of individual curves you want to grab each two neighbor curves, something like this in python:

curve_pairs = []
for each_set_of_curves in curve_sets:
for i in range(len(each_set_of_curves )-1):
curve_pairs.append((each_set_of_curves [i],each_set_of_curves [i+1]))