From BART, a San Francisco-area public transportation agency:
Organizers planning to disrupt BART service on August 11, 2011 stated they would use mobile devices to coordinate their disruptive activities and communicate about the location and number of BART Police. A civil disturbance during commute times at busy downtown San Francisco stations could lead to platform overcrowding and unsafe conditions for BART customers, employees and demonstrators. BART temporarily interrupted service at select BART stations as one of many tactics to ensure the safety of everyone on the platform.
Cell phone service was not interrupted outside BART stations. In addition, numerous BART Police officers and other BART personnel with radios were present during the planned protest, and train intercoms and white courtesy telephones remained available for customers seeking assistance or reporting suspicious activity.
BART’s primary purpose is to provide, safe, secure, efficient, reliable, and clean transportation services. BART accommodates expressive activities that are constitutionally protected by the First Amendment to the United States Constitution and the Liberty of Speech Clause of the California Constitution (expressive activity), and has made available certain areas of its property for expressive activity.
Paid areas of BART stations are reserved for ticketed passengers who are boarding, exiting or waiting for BART cars and trains, or for authorized BART personnel. No person shall conduct or participate in assemblies or demonstrations or engage in other expressive activities in the paid areas of BART stations, including BART cars and trains and BART station platforms.
I’m inclined to say that this is constitutional, because BART is government property that’s not a “traditional public forum.” (Likewise, I think it’s constitutional for a university to block wireless reception in classrooms, in order to diminish distraction, something that some public universities do.)
The restriction is facially content-neutral, but the justification is related to the content of the speech that the government is worried about — the government isn’t just trying to prevent physical disruption caused by the noncommunicative effects of cell phones, as with the restrictions on cell phones on airplanes, but physical disruption caused by what people communicate to each other using cell phones — and I think that it should suffice to make the restriction content-based. But on government property (outside traditional public fora such as sidewalks and parks), the government has a good deal of authority to impose content-based but viewpoint-neutral and reasonable restrictions. And the restriction here did seem to be both viewpoint-neutral and reasonable.
Still, it was an unusual restriction, which struck me as worth noting. Thanks to Ben Snyder for the pointer.
UPDATE: Forgot to mention — the less unusual restriction (in the last paragraph) on “assemblies or demonstrations” in BART stations is also constitutional, see ISKCON v. Lee. But the restriction on “other expressive activities” is unconstitutional, since as written it’s overbroad (talking to friends is an “expressive activity,” as is wearing a T-shirt with a message, and it’s unreasonable for BART to ban that) and as implemented it’s likely to be vague and discretionary (precisely since BART would never really restrict all expressive activities), see Board of Airport Comm’rs v. Jews for Jesus.