They recently announced their re-opening in November, I think the 16th. The roof is just one part of a big picture. They will be making more of the museum Handicap accessable, replacing the steps to the trains with ramps, and building platforms to the outside trains in the 'backyard'. The big progect though will be the construction of a new, modern repair facility that will allow for quicker repairs, minimize the jobs being sent to Strasburg PA (Those that incluse asbestos & lead paint removal), allow more exhibits space, and allow for tours of the maintinance and restoration process. There are many other changes, and it is being called the New B&O Museum.
Fore more information & pictures of the work, the museum's site is:
http://www.borail.org.