395guy explained that both people would try to call the permit office at an agreed upon date and time. Then each one could release the reservations, and somehow pick up the other permits released by the other person.
It might work if the permit office had two people answering phones and entering the released info. ...Or it might work if they had a 3-way call where both people called the permit number together.
And I am not sure (but I think they allow) exchanging dates for a reduced fee.
I think it is technically not allowed, but I have heard of one exchange where the permit holder called in and added an alternate leader's name to the reservation. Reservations can be picked up by either leader or the alternate.