It seems easy to install a Trac plugin … No idea why but I’ve experienced several difficulties before finding this procedure : I retrieve the python plugin source and create the egg file.
Most of time, the trac plugin source are available via subversion. A small checkout and you can find the setup.py file.
To create the egg file, execute python setup.py bdist_egg. You’ll find the egg file into the dist/ directory.
Take care to use the same python version than your trac server. An egg file created with python 2.4 will work with python 2.3.
Copy the egg file into the trac plugin directory (/usr/share/trac/plugins under debian). Trac will make the end of work.