I've also tryed that, it seams it uses a clientlogin token, but it still didn't work for me, maybe its a special token that only people from inside google knows
The token is passed to the browser as a URL, like this:
https://www.google.com/accounts/TokenAuth?auth=[TOKEN]&service=mail&continue=https://mail.google.com/mail&source=googletalk
where the [TOKEN] string is a really big "random" string. if you are quick you can get the full URL, but it only works once, the token expires after the first login.
I have tried using google data API to use the clientlogi token, but it didn't work