You are all right: the Ultegra BB is indeed sealed and the rust was on the outside of the BB shell. Lubed liberally now by the LBS and the sound has stopped. Oddly though, it is now neither as smooth or as silent as it was before and I am pushing to get the BB replaced, either under warranty or at my own cost.

Here's something interesting that has knocked Trek down immensely in my opinion of it: while they won't cover the BB under warranty, they sent the LBS ("at no cost" - woopee!!) a screw for the bottom cable guide that has a hole in the center. To replace the current screw and allow water to run out. Now the fact that they did this tells me they are aware of the problem and know that it needs to be resolved. Hmmmmm..... I'm disappointed because I was immensely happy to be buying a locally manufactured bike (I'm in Chicago and Trek is in Wisconsin) and proud of the fact that my bike was made a few hundred miles away. Now I'm just saddened that the one of the foremost US bike manufacturers acts in this way.