You can use your old BibTeX file, although minor adjustments could be necessary. It is prefered, although not necessary, that if your BibTeX files contain accented characters or something like this, they should be 8-bit files.
tbook's BibTeX styles (by the way, created with custom-bib) will create decent LaTeX output, but for HTML and DocBook, a filter called bibfix tries to make BibTeX's almost-XML output real XML. If you've used strange LaTeX constructs in your BibTeX file, you either have to fix the BibTeX file, or you have to extend bibfix.l, a simple flex scanner, to convert them to XML.
Another possible source of trouble in old BibTeX files is the
edition' field. Best is to use an English number in letters