I am trying to gather any information on the new light rail opening in seattle this summer.. my first big question is does any of the light rail line share trackage with the new Lake Union Streetcar?
No. The two lines will connect (at least for transfer purposes, don't know if there will be a physical connection) at the Westlake light rail station.
http://www.soundtransit.org/x1171.xml
http://www.seattlestreetcar.org/map/