Origins of Italian Tish'a B'Av trope

[ChinseG <ChinseG...>]

Yidn!
        This discussion of nusachim and folks origins etc. raises a question.  
Two-
and-a-half years ago, I attended Tish'a B'Av services at the synagogue in Rome
(the one on the Tiber, near Lungotevere di Cenci, in the old Ghetto).  It was
quite a moving experience, and ironic because it is the only time I have been
to Tish'a B'Av services or heard Megillat Eicha (Lamentations, or Come Mai in
Italian, if memory serves) read aloud.  The trope for Eicha was in the
Mixolydian mode, which was extremely haunting, mainly because it was almost
the major, but wasn't quite; in addition, the cantor did a call and response
with the congregation at the end of every pasuk, and, because they switched
off cantors every now and then, each new person inadvertently raised the key a
half-step each time he began.  (It started in a B tonic and ended up in an E-
flat tonic.)  This accidental modulation seemed to give more of an urgency to
to the questioning of God expressed in Eicha.
        But anyway, my question is, where does this trope come from?  Is it
exclusively Judeo-Italian?  Sephardic?  Ashkenazic?  (In the general sense of
those terms.)  Is it sung in the same mode in the U.S.?  I am curious, because
it's a great melody, and it would be a shame if it was strictly Judeo-Italian
and unheard outside Italy, as their Jewish community is quite small.
        Does anyone know?  A shainen dank.

-Barak Tulin