Looking through yolk source I found this:
*"The following options show information about installed Python packages. Activated packages are normal packages on sys.path that can be imported. Non-activated packages need 'pkg_resources.require()' before they can be imported, such as packages installed with 'easy_install --multi-version'. PKG_SPEC can be either a package name or package name and version e.g. Paste==0.9",
for non activated i found:
*'List non-activated packages installed by distutils or setuptools. Use PKG_SPEC to narrow results.'
and for activated: *'List activated packages installed by distutils or setuptools. Use PKG_SPEC to narrow results.'
Hope that satisfies your needs or atleast helps you ;). There seem to be very little documentation on this online.
* found in http://trac.assembla.com/yolk/browser/trunk/yolk/cli.py