In May 2012, ACE restored service to Santa Clara station. On October 1, 2012, a fourth rush-hour round trip was added, running approximately one hour after existing trips.
In December 2012, the service was rebranded from Altamont Commuter Express to Altamont Corridor Express to reflect plans for a broader scope of service.
In March 2014, ACE opened a $65 million, 121,000 square feet (11,200 m2) maintenance facility in Stockton. On July 1, 2015, management and governance of the San Joaquin passed from Caltrans to the new San Joaquin Joint Powers Authority. The SJJPA has nominal control over the SJRRC, but delegates all responsibility over ACE to the SJRRC.