The working class is barely even mentioned in Atlas Shrugged. When the union opposes Dagny Taggart's plan to operate the railroad to Colorado made of "untested" Rearden Metal, her workers support her to a man: the only workers who don't actually show up to volunteer to work on the new railroad are the ones presently working. The "communist" regime at the Twentieth Century Motor Company is imposed from "without" by those who have inherited* instead of earned their ownership of the company. Rand explicitly notes that the workers' "democracy" the new owners impose is in truth manipulated; the workers themselves are helpless pawns of the new order. (Indeed, Rand's attitude towards democracy in general is at best ambiguous.)
*Of course, Dagny Taggart and Francisco d'Anconia develop the "right" sort of values, so Rand does not consider their own inherited wealth to be problematic.
Indeed, Taggart Transcontinental appears unable to function at all without Dagny Taggart's superhuman micromanagement. This general incompetence is in part due to John Galt's sabotage, but we know from John Galt's call for the competent people remaining in society to save themselves during the collapse of civilization that Galt has not recruited everyone competent in his strike, merely the "cream of the crop", mostly (but not exclusively) those who are both at the highest level of executive management as well as having direct ownership of their companies. Rand attributes labor unrest to the action of the union leaders, divorced from the actual working class they purport to represent.
The conflict in Atlas Shrugged is clearly between factions of the capitalist ruling class. The primary antagonists are James Taggart, president and majority owner of Taggart Transcontinental; Lillian Rearden (Hank Rearden's wife), who appears to be "old money"*, Orren Boyle, head of Associated Steel and Hank Rearden's business competitor, and of course Gerald and Ivy Starnes, who inherit the Twentieth Century Motor Company. Even the minor antagonists are upper-middle-class or ruling class, with the exception of Balph Eubank, whose economic failure makes his social influence inexplicable.
*If not actually, then by adoption. Although supposedly a "self-made" man, Rand portrays Hank Rearden's mother and brother with the habits and attitudes of "decadent" old money. They in no way resemble, positively or negatively, the usual characteristics of parvenus or their hangers-on.
This narrative mirrors the situation in reality in the United States during the time of Rand's conception and writing of Atlas Shrugged: The laissez faire faction of the ruling class had lost decisively to the Keynesian, consumerist faction after the Great Depression. Even the post-war Republican party remained mostly Keynesian through Richard Nixon's presidency. The laissez faire faction, without any significant political representation, was struggling for its very identity and life within the capitalist ruling class.