It seems things have gone from bad to worse. Not only have they lied about the Acid2 test, but they've somehow managed to convince the powers that be that a new Meta tag should be supported for triggering their "standards mode".
There's an article on Alistapart outlining the details ...
http://alistapart.com/articles/beyonddoctype
The nuts and bolts of it, is that they're intending to have new trigger modes for each version of IE. So you can design a site for IE8 and not have to worry about it rendering incorrectly in IE9 as if you have the meta tag set for IE8, IE9 will render just like it was IE8 anyway. Technically other browsers could use this technique too, but they are unlikely to require it. Funnily enough, other browsers like Firefox, Safari and Opera actually work correctly without the need for special hacks to make them function. But the IE team are not capable of doing this so they have given up and are using this crude approach to solve their problems.
Here's an example of what the Meta tag would look like if it were targetting IE8 and FF3:
<meta http-equiv="X-UA-Compatible" content="IE=8;FF=3;OtherUA=4" />
And yes I am very cynical about this whole concept :P ... just in case you hadn't picked that up already ...