I harly believe in such a script. First, there are issues with tables support in LaTeX. Second, CALS tables can be very complicated. Even mature tools don't support the standard in full.
Anyway, such tools exist.
* Some time ago I wrote an XSLT for CALS to TeXML conversion. It even worked for spanned columns and rows, but I finally have thrown the script off. I'm going to try again with more powerful conversion tools, but I don't know when.
* An XSLT converter from David Hedley: http://www.vistair.com/newtbl/XSLTableCode.html
* I remember a Perl converter from SGML CALS tables, but I don't remember an URL.
The same day, now in the xsl list: CALS table model to HTML table conversion
15 Oct 2010, Update
CTAN now has the package cals, which is exactly for CALS tables.