I have this evening discovered two volumes of the Berlin Griechischen Christlichen Schriftsteller series containing critical texts of works by Eusebius at Google books. A search for “eusebius werke” brought up vol. 2.2 (HE VI-X, Martyrs of Palestine, Rufinus HE X-XI); vol 3 (Onomasticon). I’m not sure what the proper URL’s are, since I’m using a backdoor to access them: anyone?
Postscript: See the comments for links. But I have now tried entering “griechischen christlichen schriftsteller” (without the quotes in Google books). This gets me one link, here, which seems to display no content, and links to three “Other editions” in ‘snippet view’. Can anyone in the US see any of the content for any of these four?