Fortunately, an attack jet, a capacity test, a saving throw or an incoming attack jet can be beneficial for you. Lucky can only affect a jet from multiple sources as it is an attack jet, as it is the only type of jet that can be handled at both ends ( source and target); there is no such symmetric combination for capacity checks or save throws because no one can perform a capacity check or throw "at" you.
If an attacker with the lucky exploit attacks you, he can benefit from his own throw, while enjoying the same result. This is the only situation to which the special cancellation rule applies.
It is very unlikely that the cancellation rule can be used at the table because generally, only PCs have donations and PCs usually do not attack, but the cancellation rule is there to handle extreme cases. Here are some situations covered by the rule:
- Two PCs engage in player-versus-player combat.
- A PC attacks an allied PC currently under mental control that allows a backup to terminate the effect when the target is damaged.
- An NPC enemy designed with character characteristics attacks a PC.
- A PC traitor becomes an NPC enemy in the middle of a meeting.
- A PC applies Lucky to a spell attack against a spectator and misses it, and the viewer returns the spell to another PC with the lucky exploit (the Spell Reflection feature of the viewer indicates that the attack is relaunched, so it's the same attacker as the original one Lucky, the second PC could not use Lucky to avoid thinking).
There are certainly other extreme cases, and the rules for the lucky exploit allow for ambiguity and possible shenanigans by including a fix just in case.