LTSpice is meant for IC applications support and the MOSFET
models they provide are meant for the discrete transistors
such applications would want. Low voltage SOI CMOS is not
that. So Linear Tech (ADI) will have zero motivation to pull
in and support BSIMSOI or whatever. Just not relevant to
them.
If you are going to find a model that LTSpice can digest, or
a workaround using some more common model, that's likeliest
to be found in the Yahoo! LTSpice and LTSpice_Files groups.
Not sure about capitalization on the "files" one but you'll find
cross-links on the main LTSpice group page.
Maybe you should use NGSpice and your choice of schematic
front end, NGSpice has more complete / up-to-date compact
models set.