I'd like to reopen this thread. Looking at Bing today, and they have some very excellent high res imagery for the area. I usually am very suspicious of satellite imagery, but this is so good, I can almost count the logs in the log jams. I've taken some images from it and put together a trip from the last access road to the train tracks.

This is the rapids at the road, the first obstacle on the way to the tracks. If un-shootable, looks like about a 400 meter port.
The next log jam is about a kilometer past the rapids. Probably only a hundred meter port. I'm thinking these would all have to be cut, so a chainsaw would be the name of the game.

The next log jam is around 4.5 k down river.

6 k further brings one to the next jam, and then 600 meters after that, another jam.

15 k further and another jam occurs.

6k further and a short rapid appears.

4.5 k further, and the railway bridge, aka Mud River stop, is reached. Looks like there are some active buildings there.

So from the road to the bridge looks to be under 40 k, with two short rapids and five log jams. The log jams all seem to be quite short. Strangely enough, no log jams showed up in the 15 k loop where the one k port was. Probably be similar to the last leg of the Steel river past the Deadhorse Creek road. Probably doable in one long day, or two easy days. Logjams probably change yearly, but the number probably remains pretty consistent.
Just a side note, this is still the only forum where I have to resize pics. Not to sound like a jerk, but it stops me from posting trip reports that are picture heavy, or map sets of routes that we clear. Not sure what the re-size issue is, can't see it eating up more bandwidth. Might be something for the administration to discuss.