How do I keep cross-references across several documents accurate?

I think this can be easily achieved with a good reference management system (to me, SVN is great in doing this). All tex files should have in common a bibliograpghic file, and all documents should be listed in that file.

The people in charge of mantaining the T01 document, in case of a change in the bibliographic data, should update the corresponding entry in the .bib file (and the changes are tracked by svn).

So, whenever a change in the .bib file occurs, the next time the Q01 document is re-compiled, the reference updates automatically.

However, this requires an agreement on how to structure the documents' tree and the use of a versioning system. Subversion helps in both.