I´d also be interested to know what (if any) converters to VGA from Displayport that might work with Eyefinity. For example this chip looks to me like a "active" converter:
http://www.standardics.nxp.com/literature/leaflets/interface/pdf/ptn3392.displayport.vga.adapter.pdf
The line that says "While connected and powered from the DisplayPort connector, PTN3392 always reports an active HIGH Hot Plug Detect (HPD) signal to the source." would indicate at least to me that it is in fact "active" and communicating back to the Displayport on the graphics card?
Here´s another similar chip with some more technical info on it:
http://www.datasheetpro.com/node/194811
Would also like to add that I´m a little disappointed in the information of all this coming from ATI. Apart from the small print "Displayport needed" there has been little official info regarding support for Eyefinity. You shouldn´t have to dig through forums yourself to find out that some "active" DP > DVI converters actually work as well for example and that you do not in fact have to own a DP capable screen. ATI should have made it VERY clear from the start what does and what does not work in terms of adapters/converters, with all possible solutions listed.