I think so. Bufalino was trusted and respected nationally and traveled to New York constantly. He had strong ties to the Lucchese's at one point and he had power in the garment industry. I believe it's feasible. Also the Sheeran book is good but he was a hitman who wasn't exactly in the know. He drove Bufalino around but even in the book when he asks Bufalino any questions about the mob, Bufalino dodges the question. Sheeran wasn't nearly as trusted as guys like Ed Sciandra, Guv Guarnieri, or William D'elia, who got to discuss business with other families. The result is a kind of messy book that tells you more about Jimmy Hoffa and Angelo Bruno then Russell Bufalino. I was kind of frustrated reading it.

Anyway. I can't say about Bufalino being interim boss but seeing as how everyone liked him and he made weekly trips to Manhattan, it's possible.