Complex sentence: When Mortier abruptly left the New York City Opera in 2008, the project was left in limbo until Mortier took up his new post as General Director of Teatro Real in Madrid, bringing the "Brokeback" project with him.
Split into simpler sentences: When Mortier abruptly left the New York City Opera in 2008, the project was left in limbo. After he took up his new post as General Director of Teatro Real in Madrid, he brought the "Brokeback" project with him.