I was not the person who posted in the results section, but I received a phone call from UW at a similar time (last Friday) also telling me I was accepted. However, they told me that they had made an *early* decision about me. Then, they told me they hoped to get me the official details by next week. However, to me, it sounded like they had not even made all their decisions (or even most of them), so I don't think they will be giving everyone their official details this week - I would assume it will just be for the people they called (which is, I believe, a small subset of the people they will eventually accept).
As for CMU, I believe they called or tried to call many of the people who were accepted (I missed a call from a number, which I later looked up to be the cell phone of the CSD head). Then, I think, I received an email (from the CSD head) with the official details, including an attached pdf of an official letter of acceptance. I did also receive an email from my faculty contact after that. Unfortunately, I'm guessing this all means that the CMU results are, in fact, official, unlike the UW results, which seem to be an "early" wave.
Just my thoughts.