Here’s a bit of Labor Day irony. The man who led the historic 2005 bus and subway strike—which forced millions of commuters to squeeze into packed cabs, pedal bicycles they hadn’t used for years and hike to work like intrepid Boy Scouts—is now a licensed cab driver. Roger Toussaint, the fiery former president of Transport Workers Union Local 100, got his permit in December to drive a taxi in Cobb County, Ga., where he now lives, records show. “Driving a cab is a dignified profession,” Toussaint, 55, said during a telephone interview last week. …