Here is what I’ve been able to find so far on the c-span site. They have a link to “Green Party Presidential Candidate” on the right sidebar on their home page:
Green Party Presidential Candidate
Product ID: 206375-1
Last Airing: Not Yet Aired
Event Date: 07/12/2008
Location: Chicago, Illinois
The 2008 U.S. Green Party National Nominating Convention was held in the Chicago Symphony Center. The acceptance speech of their presidential candidate was shown.
So it looks like it *will* be aired, they just aren’t saying when yet.