Railroad bridge identity question.

Anybody know what bridge is pictured on page 39 of March 2005 Trains? it looks like quite a bridge and would be interesting to know more about it. It would and really interesting model to take a swing at kitbashing.

Also, anybody know how they work? Counterweights? How does the track line up when they set it back down?

Thanks!

Try posting this over on the TRAINS magazine forums. Someone is sure to know.