Pretty much everyone will want to be in the set of results that come up first when you search for something, and the cost of making something with AMP is really, really low. People could knock up a quick prototype very early on.
I expect that they've worked with people to figure out what makes the most sense to actually build and so the BBC and Buzzfeed would have had a bit of time before the announcement to start making the pages.
I expect that they've worked with people to figure out what makes the most sense to actually build and so the BBC and Buzzfeed would have had a bit of time before the announcement to start making the pages.