MathType to Plain TeX

We are engaged in producing math textbooks for a major publisher in Italy. In our workflow there is a stage in which we substitute math formulas (usually created with Equation Editor) in the MS-Word files provided by Authors with the appropriate TeX code (Plain TeX plus a small set of macros borrowed from LaTeX, actually). Language issues should not be a problem (we publish in Italian), as the very work regards only math notation. Please don't use any sort of RTF-to-TeX converters that are more trouble than they are worth: the cleanup of their output is often on a par with the amount of effort needed to re-key the original. What we need is a MSWord file (the same as the original for the textual part), where math formulas and notations are converted to clean, reusable, PlainTeX code.