Haven't been in that situation, but, a trip picked up by PDO bump should be droppable. 25.L.9.a states that the PDO bumper has trip guarantee and (essentially) the only trips you can't drop are those for which you don't hold guarantee.

Hmmm......let's review the aforementioned statement for accuracy.

PDO Bumper = person bumping another pilot for the trip
PDO Bumper = does NOT maintain trip guarantee
PDO Bumper = paid Per Diem Only for trip


PDO Bumpee = person bumped off of trip by another pilot
PDO Bumpee = maintains trip guarantee
PDO Bumpee = loses the Per Diem for trip
PDO Bumpee = celebrating the fact the he is paid for not working a trip

If a mutual PDO Bump is to occur, then each PDO Bumper only attains the Per Diem Only for the "new" trips; each pilot retains the trip guarantee for the original pairings. As such, cannot drop/trade the "new" trip.

Now, if we only had the actual wording from the contract, things would be much more clearer.