Here is a link to the King County page about the BNSF right-of-way and a discussion of the background of the deal and its status as of Spring 2006. Here is the 2004 report of the eastside corridor advisory committee. Here are the links King County included in their newsletter when the deal was anounced in 2006.
Here is the article reporting the initial deal approved by the Port Commission
Here are some subsequent articles that I thought were worth preserving.
Here is the most recent article.