Earlier in the thread someone mentioned the idea of BNSF using the Snoqualmie Pass (MILW) tunnel in favor of the Stampede tunnel. I believe the MILW tunnel would handle double stacks as is since it was lowered for tri-level auto racks with clearance for the electrification, however, as I understand it when BN gave up on the line and pulled it up the line was turned over to the State of Washington to add onto the John Wayne trail system. I do recall the State of Washington working with a pipe line operator to locate a natural gas pipline though the tunnel and under most of the MILW R of W over the Cascades as wall as a fiber optic line under the R of W as well. If indeed a pipeline was located though the tunnel, then relaying track isn't an option. After reading a history of the construction of the Stampede tunnel, I think that messing with it very much could turn into a costly operation with the best bet to be lowering the floor. It might have been cheaper to use the MILW tunnel if it were available, but the line was disposed of during BN's "short sighted era" when the SP&S was also lost.