Your thinking is correct but ASA1600 on Blackmagic Cameras is basically ASA800 + 1EV of digital gain, so it isn't really all that usable due to FPN and dramatically increased chroma noise and all sorts of nastiness.
ASA800 offers the best bang for buck in terms of highlight protection.
Above ASA800, the Canon cameras apply analog gain, so the performance should be considerably better than what BMD is offering at high ISO settings.
Now, not to be rude or anything but your question doesn't really make sense, seeing as how the dynamic range of "Canon RAW CR2 files" differs from camera model to camera model (if you are asking about the actual file format itself and how it differs to CinemaDNG...that's well above my pay grade ^_^ ).
That being said, as a piece of anecdotal information, compared to my 5D MarkIII using Magic Lantern RAW video, the BMCC had more dynamic range and offered a cleaner image up to ASA800.