The other day, I learned that the Prius will still switch to EV mode while in cruise control at 55-60 MPH. I don't see it go into EV at higher speeds with CC on, though I didn't really play that much with it.
I just revived my diagram that happened to be derived partly from what bwilson4web had provided. My diagram was made using Flash, which is no longer supported in modern browsers, but I've rewritten it in javascript: http://eahart.com/prius/psd