I will check with Hank at MARC.
One more followup. I emailed with Hank at MARC (marc.theaimsgroup.com). Hank really likes the idea and tried enhancing the patch to cover MARC as well. He ran into a few issues that caused him to abort the attempt ["...setting of the List-Archive: URL header. MARC (and I think Gmane too) sometimes takes liberty with list names, such as for a project foo, if they've a list "users" we add it as "foo-users" (as opposed to Mail Archive's equivalent "email@example.com" which works to keep them unique). That also makes it difficult to make meaningful predictions for what the resulting URLs will be, or checking the subscription list, etc. "]. So for now Hank is passing on resolving those issues, although he's willing to put more effort into it if people want the MARC option.