There is this featured thread over at WebmasterWorld named How to Remove Hijacker Page Using Google Removal Tool. The thread creator proposes one method to help remove a URL (hijacked) from the index. He proposes that you added the "noindex" meta tag to the page being hijacked, then go to the remove url page at Google and enter in the hijacker's URL, you should get a message saying it will be pulled in 24 hours, and finally remove the "noindex" meta tag from my page.
Claus replied to the thread on the second page, Claus was the person who wrote the detailed explanation of the page hijack, saying:
Just dropped by to say that you can also serve a 404 or 410 code, that works just as fine. (no need to serve it to all, just do a little .htaccess magic and serve it to Google for a few minutes, then take it down again)
Claus then adds that this whole concept does not solve the issue, Google must solve the issue.
There is one more reply I would like to quote, which seems to work as well, and that is by nuclei. He says:
Simply use mod_rewrite to redirect anything coming from the site that has 302'd you to a page that basically says that site is stealing other peoples rankings using a known google exploit, and submit the page to googles addurl. I am quite sure if that was done by enough people google would fix the issue quickly. Also doing so would stop that page from ranking using your ibl's and keywords.