I was recently reading a ride report from someone who recently traversed the west section of the Iron Horse State Park (John Wayne Pioneer Trail) from Rattlesnake Lake to just east of Hyak for a biking and fly-fishing trip. It's not every day that people write up detailed reports about the trail. Russ and Laura did a great job documenting their trip. I hope someday I can meet "Steve," who they mention has researched and written quite a bit about the JWPT.
This write-up led me to bikingbis.com which talks about tunnel repairs being done in Iron Horse State Park by WA State Parks...
Tunnels 48 and 49 will reopen soon (July 2013?) while tunnels 46 and 47 and not being repaired. A quick visit to the State Park Website explains that, what the tunnels are still closed, riders can pass through them if they sign a waiver.
Without the waiver it is a 15-mile detour around the tunnels using local roads, which would mean you skip the Yakima river canyon between Thorpe and Cle Elum. I think I know the option we will be using. }B^)
UPDATE (12 July 2012): Tunnels 48/49 are OPEN! Also, the Rails-to-Trails Conservancy did a great piece on the tunnel repairs last December, which I evidently missed.