I assumed you meant the wheelchair not the seven icons.
The thing is most screen readers can be set to read the title attribute and the logo itself isn't that important it's not a graph or a chart.
I'd agree it was a stupid idea that a longdesc appear on a new page; just think of a photo gallery each time you linked on a small thumbnail you'd be hopping backwards and forwards.
I still stand by: http://www.stuffandnonsense.co.uk/archives/accessibility_footnotes.html#comment6
Even though Joe Clark had some spaced-out idea; 1024 characters for a title attribute was fine!
By convention, limit alt texts to 1,024 characters (1 K) or less.
(note this full post uses about 1024. characters with spaces).
"Graphic shows icon symbols of range of diverse disabilities."
Would be good enough since the image is more decorative than meaning to the blind-user. Now if you used the icons throughout the site next to text than maybe a long description would make more sense.
Again you have to consider not all users are blind that have issues with images.