In Seattle, the Sounder Link light rail uses the former UP / MILW passenger lead Right of Way South from the transit tunnel @ Seattle Union Station, for about 2 miles to just South of Lander St., at their maintenance shops. The ex - passenger lead still has an industrial lead in place for part of the R of W, however I don't believe it is in use and it is separated from the light rail by the 5th Ave. South Metro Busway.
The proposed Northern extension of Link light rail may use a bit of the old Seattle - to - Everett Interurban right of way in Lynnwood, though the wetlands around Scriber Lake have become an issue. As well, one of the proposed routes for the East extension of Link light rail through Bellevue would use a bit of the BN Woodinville Sub R of W,( now OOS ) once the route of the Spirit of Washington Dinner Train.
In Seattle's South Lake Union area, the SLUT Streetcar runs on several streets that once held Northern Pacific industrial trackage; however all NP trackage in the area had been OOS and disconnected from any BN trackage since at least 1995, when I moved to the area. During construction of SLUT several old NP tracks were " discovered ", leading to delays during their removal.
In Tacoma, the Sounder heavy rail commuter trains share the ex - Milwaukee trackage, now owned by Tacoma Rail, from TR Junction on the BNSF, to Freighthouse Square station, where TR continues up " The Gulch " to Frederickson and Centralia, while Sounder uses a new connection to the ex - NP Prairie Line up along South Tacoma Way to Lakewood. I understand that Tacoma Rail only operates this shared trackage during the midday and at night, when Sounder is not running.