The bus-driver was whistling, perhaps in anticipation of his wife, who would be a woman with ample breasts, those of a realized maturity.I read (past tense) that sentence as a future -- his wife whom he would someday find and marry. But the next sentence recasts it into a subjunctive (or conditional? grammar mavens?) in the present: the narrator imagines him as currently having a wife, who must perforce be bodacious. I go back to re-read and find again that word "anticipation," which threw me so to speak into the future, but the driver may merely be looking forward to getting home to his extant wife. In English, "would be" seems to allow for both. It's a beautiful oscillation of future and fictional present with which to start a novel.
(Third paragraph, confirming that the first sentence is about fictionality: "Was he, after all, a bachelor, perhaps even some mad Don Quixote... and his family life, an emanation of my over-active imagination...?")