I guess one must ask El Reg to write about it. I think that might have been how it got solved a couple years ago when comp.lang.c and others were affected by this [1].
Currently, at least mozilla.support.seamonkey (not a USENET group, but from news.mozilla.org - which was shut down, but whose archived content would certainly be useful) is in that state at Google Groups. And yes, IIRC the only SPAM in recent times in that group had been posted via Google Groups...
What about the newsgroups where access (including the archives!) had been blocked by Google for too much spam (maybe ironically facilitated by Google Groups in the first place)?