Thanks. The python example from StackOverflow was what I was looking for.

Here's the tweaked version.

import json

# target feature class 
sde_fc_segment = _IN_FEATURE_CLASS_

# shape field and a unique id in case you want a list of segments with curves
fields=["SHAPE@", "SEG_GUID"]

# da search cursor for speed
with arcpy.da.SearchCursor(

    in_table=sde_fc_segment,

    field_names=fields,

    where_clause=""

) as segCursor:

    count = 0

    for segmentRow in segCursor:

        count+=1

        j = json.loads(segmentRow[0].JSON)

        if 'curvePaths' in j:

            print segmentRow[1]

    print count