Ulrike,
\lccode`\^^[=`\^^[ % oe in OT1
\lccode`\- =`\- % default hyphen char
\lccode 127=127 % alternate hyphen char
\lccode 23 =23 % textcompwordmark in T1
\InputIfFileExists{hyphen.cfg}
There is no sensible hook for xelatex.ini.
Then clearly it must be fixed in hyphen.cfg. Right now I was
preparing a new version of babel and this issue (and another
related to luatex) is in the todo list. It will be available
in two or three weeks (or so I hope).
Javier
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