Hi Martin,
I'm looking into the SQL ST functions for curved data. In the immediate, can you use the JSON via the da.SearchCursor?
for row in arcpy.da.SearchCursor("SDE.ST_LINES", ["SHAPE@"]):
print row[0].JSON
Output:
{"curvePaths":[[[-43050711.692462206,8862199.7932373881],[6561666.6665721536,39487124.706322819],{"c":[[99048939.903926104,89099503.065357178],[43156100.269598193,82281334.322446659]]}]],"spatialReference":{"wkid":102645,"latestWkid":2229}}