After that discussion died down, our friend Micheal arrived with a very good answer.
See it after the jump.
The Midrash (and I) believe that every physical reality has a spiritual counterpart - often referred to in Midrash as "mazal" or "sar". Furthermore, Midrash (and I) believe that the books of the Torah, even those written by Isaiah, and other, lower-level prophets, actually pre-exist their authors, because they are part of Torah which is derived from the will and wisdom of G-d, which, (per Rambam) is one with G-d, who pre-exists all of creation. This is expressed in the Midrash with allusions to the Angels studying the Torah. What the Angels study is the spiritual counterpart of the Torah that exists on every spiritual level, in a different form. The Angels study the spiritual level of the Torah as it exists in the worlds of Gan Eden Elyon, or Gan Eden Tachton, depending on their level. R' Chanina here probably is referring to the Sarim of Pharaoh and his advisers conversing about how to destroy the Jewish people. The Isaiah they quote is the spiritual Isaiah, that exists before creation.If we let our eyes pass over the hippie nonsense about "spirituality" and the laughable suggestion that "midrash" is monolithic [i.e."the midrash (and I) believe "], Micheal's answer is a very good, non-apologetic solution. And its even better when we remember that the original drash does not say that Pharoah and his advisers are the speakers. That's an assumption on the part of the reader. The Midrash merely informs us that something was said.
The only problem I can see is this: Angles plotting against God sounds awfully Chistological to my late-modern ears. Now, I acknowledge that much of this sensitivity is the Rambam's fault. He's the one who convinced Judaism that angles are God's servants, not his antagonists. Pre-Ramabm I suppose it was possible to speak of angles as independent actors, just as it was possible to speak of a corporeal God. Moreover, what we think of as the Christian idea of Satan as God's personal Lex Luthor probably was derived from a Jewish source. Still, I'd like to firm up Micheal's answer: Does anyone have an example of a Tanna telling a story about angles going behind God's back with neither His knowledge nor permission? Bonus points if the Tanna was Rabbi Hanna B. Hanina.
One other thing: Its possible this drash does not originate with R. Hana. Often, teachings quoted on the pages of the Babylonian Talmud can be found with slight differences in Jubilees, or Ben Sira, or the other apocryphal works known to us from the Dead Sea Scrolls. Sometimes these differences are subtle, and at first glance irrelevant; at other times the older parallels shed much light. If such a parallel for R. Hana's drash exists, it might clear up this question. I'll see what I can find.
Search for more information about the many ways midrash disagrees with itself. at 4torah.com