The cynicism, pragmatism and moral ambiguity underlying B7 represents a step towards the levels of social realism that pervades cyberpunk. And of course, the gloomy, dystopian vision shared by both, with no promise of happy endings or successful resolution. It diverges from cyberpunk in a number of ways. Cities hardly ever features in B7, and the crew never went out into the streets to mingle with the masses. There were, of course, very practical production reasons for this.
Youth culture has a high profile in cyberpunk fiction.
Gibson's first two novels are essentially 22nd Century thrillers. So, B7 was not cyberpunk. It was made too early for one thing. Even if it had been made several years later, it still wouldn't have qualified. Television is too conservative a medium, and has enough trouble with science fiction as a basic concept.