Nope.
The old railroad used a lot of tressles to span across the Tiekel and a few other V notched streams. Some places the mountains go right down to the water and are steep and overgrown with alder and willow. The tressles have collapsed for the most part. Some of those streams can't be crossed unless you go higher up in their valleys. It would be one heck of a bushwacking job just hiking. No way you could do on a motorcycle. Least not until the trail or road gets punched through. If the trail does ever get punched through, I don't know if the trail will be open for motorized use or not.
The Tasnuna can't be crossed near the Copper, too big and too swift. Most of the old railroad grade is gone, washed away. The road does extend northward from the Million Dollar bridge for a little ways, but is impassible by a couple of streams, then the road bed is nothing but alder and willow. The construction crews aren't finished with the Million Dollar Bridge yet, either and probably won't let anyone pass until that is completed anyway.