(This issue got overlooked for far too long.) If you're still interested in having it included, I would appreciate a link to the part of SPIP (either code or documentation) that defines this format. Do the files really use .html as the extension?
In general, SPIP is ill-documented in English (French docs are somewhat better, still not great) and it can be a pain to work with. (There are also several issues in the code, which has been moved to http://zone.spip.org/trac/spip-zone/browser/contribs/pygments. I can better comment on those when a pull request has been created.) However, in general this looks like a nice addition.
Yes, It really use .html as extension. The two links of Camil explain the syntax, and are covered 90 % of the code. But for the need of developing this module, I used http://programmer.spip.net/ and all the fragment of code where well formated.