I'm not certain which Planescape Metaplot you're referring to; there were several plots that ran through the series. The rise and return of Orcus (as Tenebrous) begins with the Great Modron March and is concluded in Dead Gods. Uncaged, Faces of Sigil detailed several plot threads, such as the celestials of the upper planes working behind the scenes to supply weapons for the Blood War in an attempt to keep it going. That plot thread was expanded greatly in Hellbound: The Blood War. Many many adventures and supplements, such as the Factol's Manifesto, detail the faction cold war in Sigil. In turn the conflict comes to a head in the Faction War adventure. In short there's no single Planescape metaplot and, in essence, most supplements and adventures build upon each other. Don't know if that answers your question though. :\