I have spent some time comparing low level WP_Http results against wget results and have come to the conclusion that Google Cookies aren’t being passed through the series of redirect which happens when viewing a Google Form with the new URL scheme.
Unfortunately I am not sure what to do about it yet. The usually very helpful WordPress Hackers mailing list is surprising quiet right now. I am trying to figure out if I can “remember” cookies and pass them along each time a redirect happens. I am reasonably confident that is what is needed however making it happen within the WordPress context is another story!