1-800-OK-CANON (in the US), which is 1-800-652-2666. Yeah, nice number Canon.
I followed the prompts for general information.
The lady I spoke with told me that the 5Dm3 was going to be available on the 26th. Then she said the 16th of March. Then she said the 26th again. I explained that several stores in the US already had them, and she said "that is shocking."
So, even Canon, or at least this lady at Canon, has no idea what is going on.