The translator for the Origen homilies is really doing an excellent job. He ‘s been looking into the issue of why the excerpts from catenas printed by Baehrens in the GCS are shorter than those printed by Migne (reprinting the Delarue edition).
Translating some of the latter reveals that they contain material evidently not by Origen; indeed disagreeing with the Origen material that they quote. Baehrens gives a reference to Faulhaber, Die Propheten-Catenen nach rom. Hss. (= Bibl. Stud. 4, 2.3 ) , which is actually online at Google books (for US readers). Biblische Studien IV is here.
Faulhaber lists the 233 fragments by Origen on Ezekiel on pp. 153-5, and states that these are taken partly from the Homilies, and partly from Origen’s scholia on Ezechiel. He also notes (p.154) that the material in Migne is often plainly from the Homilies, but needs further study. It seems that Delarue had a catena manuscript rather different to the others.