The growing network of commuter buses that shuttle workers between San Francisco and Silicon Valley has become the target of increasing protest in recent months, and now it's subject to a legal attack as well.

Tech companies like Apple and Google, as well as the mayor of San Francisco, the SF Muni board, the city planning department, and a variety of bus companies, were all sued yesterday. The lawsuit claims that the city's pilot program to allow the buses to operate should have passed through an environmental review, of the same type done when city transit programs expand.

The suit is an attempt to bypass the San Francisco Board of Supervisors, which approved the program on an 8-2 vote last month. Activists threatened to sue on environmental grounds if they lost that vote, and now they are following through on that threat.

Shuttle buses have long used city transit stops under a "handshake deal" with Muni, San Francisco's public transportation system. The commuter bus system has grown in recent years and now consists of "35,000 boardings a day, 350 buses and over 200 stops throughout the city," according to a lawyer for the activist groups who spoke to Re/code after filing the suit.

Of course, that lumps together a lot of different shuttle bus programs. It also seems hard to dispute that it's a net environmental benefit, since many of those 35,000 trips—more than half, according to one small study—would be taken in private cars if the buses weren't around.

The lawsuit seems to be the an attempt to fit the biggest policy concern, the Bay Area's rising housing costs, into an environmental box. Lawyer Richard Drury, who filed the suit, told Re/code that's perfectly legitimate move. "People don’t usually think of rising rent in terms of environmental impact," Drury told Re/code. "It’s a little more unusual than air quality or traffic. But it’s actually written into CEQA [California Environmental Quality Act]. It asks, 'Does the product displace substantial numbers of people?'"

"These buses are having devastating impacts on our neighborhoods, driving up rents and evictions of longtime San Francisco residents," Shortt told the SF Examiner.

The plaintiffs include a new group, the "Coalition for Fair, Legal, and Environmental Transit." Other plaintiffs include the Service Employees International Union Local 1021, and Sarah Shortt, a tenant advocate with a group called Housing Rights Committee.

A regional business group issued a press release condemning the action. "This lawsuit continues a misguided and misdirected campaign to blame employee shuttles and the tech industry for the serious housing crisis that is afflicting San Francisco and other parts of the region," said Jim Wunderman, President and CEO of the Bay Area Council. "Attacking employee shuttles misses the target completely."

Several city agencies are named in the suit. A spokesman for the SF City Attorney's office told Bloomberg he hadn't read the suit yet and couldn't comment.