Two years ago, what is now the third-largest worker-owned cooperative in the United States couldn’t get more than a dozen people together. That might be hard to believe, because they all have their own transportation. They’re cab drivers. It was early October, notoriously one of the most uncomfortable times of the year in Austin, Texas, when the temperature often still reaches 100 degrees Fahrenheit. Victory seemed out of reach then for the Taxi Drivers Alliance of Austin, which had convinced about 20 percent of the city’s cab drivers — mostly older immigrant men, from Ghana, Sudan, Jamaica, Pakistan and many other places — to pay annual union membership dues. Because drivers are classified as independent contractors, taxi unions often have trouble getting traction. But times were especially tough for drivers in Austin, who were having trouble competing with Uber and Lyft — which were operating openly (and illegally) in defiance of local laws — and squeezed by the city’s three cab companies, who charged each driver around $280 per week just for the permission to get behind the wheel, to say nothing of the costs of actually leasing a taxi and putting it on the road. And because of the competition from Uber and Lyft, cab companies were raising their fees on drivers to make up for lost revenue.