Volume 11 and Volume 12 are for download in #manga-translation on irc.irchighway.net

I bought Volume 11 while over in Japan, but Volume 12 won't be collected until late Summer. Their are people who are still scanning the biweekly chapters though. Tenjo Tenge comes out twice a month as opposed to four times a month. This gives them more time to put more detail into the art.

The first two chapters of Volume 11 have been scanslated already. They are on that first link where you got Volumes 1-10. http://tjtg.mangatranslation.com/downloads.html
They are on the top of the page.

Here is where you can download the raw files for Volumes 11 and 12 - http://www.jojohot.com/

Its a japanese sight, so good lucky finding it there, but I know they have them there.

Also the webmaster of MangaTranslation.com puts up his text translation the Volume 11 ones can be found here.

http://tjtg.mangatranslation.com/TJTG_11_Trans.html

That link might be dead now though.