Here is the issue, :

whenever we enter "Å“" (oe ligature) in a content object, the corresponding URL Alias contains "ae" (ae ligature) whic is wrong. The problem comes from the transformation table which does not map to the correct char.

Wikipedia page with some related information:
http://en.wikipedia.org/wiki/%C5%92#.C5.92_in_different_languages

U+0152 = Å’ = "OE", not "AE".
U+0153 = Å“ = "oe", not "ae".

more info:
http://www.fileformat.info/info/unicode/char/0152/index.htm

from eZ Publish (4.0 stable)/share/transformations/latin.tr:

*snip*
latin-exta_transliterate_ascii:
U+0132 = "IJ"
U+0133 = "ij"
U+0138 = "k"
U+0149 = "'n"
U+014A = "N"
U+014B = "n"
U+0152 = "AE"
U+0153 = "ae"
U+017F = "s"
*snip*

trunk version of this file has the same entry.