Interestingly, the positions A2-A4, A2-A5, A2-A6, A2-A7 and F9-FA, F9-FB, F9-FC,F9-FD are all blank in the CP950 table printed in Nadine Kano's Developing International Software for Windows 95 and Windows NT (1st Edn), a Microsoft Press publication from 1995. The unification of these characters with others of more or less similar appearance thus seems to have happened relatively recently in the history of CP950, possibly because approximate Unicode mappings were considered better than none, and Han characters must have been more of a concern than box-drawing characters for users of Big5 and Traditional Chinese.
It is my understanding that pre-Unicode Big5 fonts customarily included the E-Ten extensions and that the box-drawing glyphs were similar to the ones shown in Lunde's table. The attached screenshot shows how the characters in question appear in a bitmap font which can easily be found by searching for taipei24.bdf.gz.
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Finding additional documentation in the form of fonts and printed tables should not be too difficult for someone who can read and write Chinese. As pointed out by Dr Freytag, demonstrating current usage could be considerably harder. Øistein E. Andersen
