Some of the 92,000 people employed by the University of Pittsburgh Medical Center (UPMC) are on a one-day strike today, demanding a starting wage of $20 an hour, safe staffing, affordable health care without medical debt, and the right to form a union without interference.

It poses a dilemma for the health care giant that once claimed to have no employees. That argument was made when the City of Pittsburgh challenged the hospital system’s tax-exempt status nearly a decade ago; in response, UPMC insisted that its workers are actually employed by subsidiaries. (It didn’t take long for the city to find federal 990 tax forms filed under the name “UPMC Group” that listed more than 50,000 employees.) The legal maneuver faded from memory when Pittsburgh mayor and inveterate squish on workers’ rights Bill Peduto dropped the challenge, though with mayor-elect Ed Gainey vowing to take up the fight to revoke UPMC’s nonsensical nonprofit status, it may soon be back in the news.

In reality, UPMC is Pennsylvania’s largest private sector employer, and the people who are on strike are some of its lowest-paid workers. They are part of a years-long organizing effort with Service Employees International Union (SEIU) Healthcare Pennsylvania, which also represents nurses at several facilities in the Allegheny Health Network (AHN), the area’s other hospital system.