In April, 2011, the MP 89 CC #01 was moved to Line 4, as work to fully automate Line 1 was nearing completion. The transfer of these trains to Line 4 will allow RATP to retire the MP 59 stock, which are reaching the ends of their useful lives. After various internal components (such as the automated station announcements) were updated to accommodate service on Line 4, train #01 went into service on May 23, 2011. Until September, 2011, train #01 was the only MP 89CC train to operate on Line 4. On September 10, 2011, train #44 went into service, marking the second train to be transferred. As the new MP 05 rolling stock began to debut on Line 1 during November, 2011, more MP 89 stock was put into service, allowing the RATP to transfer two to three trains per month.