A feature request for integration with Joomla! was posted here: http://dev.tiki.org/wish2166
I think tightly integrating features would be a lot of work and hard to maintain. But there could be loose exchange of data between the apps (ex.: RSS) and a common login.
Tiki supports many: http://doc.tiki.org/External+Authentication
There is even one for phpBB: http://doc.tiki.org/phpBB+Authentication
Token Access (as currently implemented) is not what you are looking for:
If you could make something similar for Joomla!, it would be awesome. Please do share back these enhancements: