Mirra is the last guy that would be an informant!
The lengthy sit downs that took place over who "owned" Donnie Brasco were known by all in the Bonnano family.
They figured that Mirra had played a part in bringing Donnie into the family and lets face it, NOBODY liked the guy, Massino had a legit reason to whack him.

Just as a side piece of info.
Got to 115 Maddison street on googlemaps and Mirra's former place the bus stop luncheonette is now a Chinese takeout.

Leftys old social club is a nail bar (43 Maddison street)