Remember that the meeting was arranged by George Paglieri, who at least in the 10 second phone call they portrayed as on good terms with the Soprano family. So to dismiss it as simply "off the record" might be a bit of an understatement. Since its doubtful that Phil was the most powerful boss in NY at the time, it seems reasonable that Tony could have gotten the support of The Commission. We don't even know what the status of The Commission really is in that world, could be like LCN today.

Its unrealistic by real standards since we know how powerful the Decavalcantes were, but as has been pointed out The Sopranos were portrayed as being closer in stature to NY. Not equal by any stretch but they were firmly in control of North Jersey.