i don't see how massino or anyone else could have thought that mirra was in on it from the beginning and helped brasco infiltrate the family because when he got out of prison he had a series of sit downs over donnie brasco where he lied about brasco stealing 250k from him in a drug deal, the obvious motive being convincing the family that donnie should be killed. no informant would be dumb enough to do this to his FBI handler.

for this reason i (and probably massino and the rest of the bonnano higher ups) wouldn't believe that mirra knew that brasco was an agent, let alone brought him into the family as an undercover.