There’s movement in the standoff between the Massachusetts Museum of Contemporary Art and Swiss artist Christoph Büchel, who left his war-themed installation there unfinished last December after relations with the museum soured badly. “On Saturday it will open the doors to the show anyway, without Mr. Büchel’s permission or cooperation. But there is a catch…. Because of concerns about legal action by Mr. Büchel, the museum will shield all the huge objects in the warehouse from view with tall plastic tarps, as if Christo and Jeanne-Claude had intervened at the last minute.”