Another point (as long as we're speculating, which is one of the joys of these boards ): Just suppose that Tessio saw himself and Clemenza as rivals. If he did, the fact that the Don's shooting occurred on Clemenza's watch (Paulie was a Clemenza man), and that Sonny wasn't entirely trusting Clemenza at that point, played in Tessio's favor. Therefore, it'd be in his interest to have nothing go wrong at the hospital, the better to prove his trustworthiness at Clemenza's expense. The last thing Tessio'd want to do would be to engineer a screw-up at the hospital. No, I think it played just the way Goombah said.