We have (ArM5 p.105):
A maga may, at any time, invest powers in the familiar bond. This is a laboratory activity, and the rules are the same as those for investing a power in an invested device, with five exceptions. < exceptions not relevant for use in an Aegis >
We further have (ArM5 p.161):
Effects from enchanted devices are resisted by the Aegis unless the item was within the Aegis at the time of casting, or was created within the Aegis by someone who was part of the ritual or in possession of a token.
So the effects enchanted into the familiar bond interact with an Aegis like effects from a device. As that device is the familiar bond, it is resisted by the Aegis "unless the familiar bond was within the Aegis at the time of casting, or was created within the Aegis by someone who was part of the ritual or in possession of a token."
Where is the familiar bond, if magus A is outside the Aegis and his familiar inside? It is most plausible, that it is not fully inside "at the time of casting".
But magus A could still have instilled the power into the bond, while within the Aegis as participant of the ritual or in possession of a token. In that case the Aegis would not resist.
By ArM5 p.161 the Aegis would otherwise resist effects in the bond to A's familiar inside the Aegis, if A triggers them from outside and has no valid token for the Aegis.