How does that weapons swapping actually work with certain passives?

Situation: i have two croosbows, one for bolts(A), other for grenades(B).
On skill tree A i had speced into damage against low life, on skill tree B i have grenade area of effect, damage, and repeating explosions.
Question: If i shot a bunch of grenades with set B, then swap back to set A, do does shot grenades regain abilities from tree B, or they instantly lose it? And if its the latter, is it a permanent loss, or until i switch back to set B?
Also, does those shot grenades gain damage on low life bonuses when i switch to set A? That would be kinda absurd, but i'm literally guessing here.

Where you ever able to discover how it works by now? I'm pretty much in the same spot, just that you can copy the main weapon now.
Im pretty sure it works like this:

Set A gives your grenades buffs
Set B gives your bolts buffs

If you throw grenades with Set A, and then trigger with Set B, you lose the grenade buffs, since Set B is active.

Sorry for necroing this thread, just want to confirm if grenades retain their buffed state once out, or if the buffs must be active once they explode.