Hi Georg,
the only thing I could find on the net is a reference to:
"\begin{tabular}{p{1in}p{2in}}" at
http://www.cs.cornell.edu/Info/Misc/LaTeX-Tutorial/Tables.html. Assuming
that one knows the effective width of the whole table, one then should
be able to calculate the width of a column based on previous information
in the *.rst files. Since I really don't know anything about LaTeX - and
you certainly do, I should better shut up and don't say anything more.
But indeed, this table business in LaTeX seems to be a bit messy.