There was an information session for the residents of avenue de la musee at the museum premises as they'll be affected the most by the expansion work. Officials from the museum and the city were there as well as the architect. They said that the street will be closed off from april 2009 for about 9 months as I recall, which is the time they need to build the tunnel, which will also double as a gallery. During that time the street will be a two way cul de sac.
Demolition of the church annex is scheduled to start soon. They also said that the church facade will be cleaned in two phases over the coming 2 summers, so expect less contrast with the white marble that's going to be used on the new extension.
The public space surrounding the church building will have outdoor sculptures just as the ones on the other side of the street. The plan is to complete all the work by december 2010.