Further the above reply, if you collect a 4-5 sets of Hlin in delt mode, after resyncs of the connection a day or so apart, you can check whether the number of tones per 2pi change in phase changes. Normally it does but you can get same value a few times running. Currently you have about 13 tones. If that number changes then nothing could be deduced. Equally unless the actual line length 4km nothing is worthwhile. Even then Hlog is going to give a much more accurate info on line issues such as bridged taps. The evidence is that all that Hlin could give is an indication of the line length and that estimate can be done by hand counting the number of tones per 2pi. In short really don't think any other analysis is worth doing.