BART shut down mobile phone service during planned protest, digital rights groups say. BART says it cut service to protect passenger safety, not to stop a protest. The FCC is looking into BART’s decision to cut mobile service on Aug. 11. BART: Protestors had planned to chain themselves onto BART subway cars, potentially trapping more than 8,000 passengers in a 3.4-mile tunnel at the bottom of the San Francisco Bay. BART president: An emergency situation in a trapped train would have been difficult to respond to.”]