Unfortunately, this is a situation where it is up to the first person entering to be honorable and put the second Will Call ticket in your name when he gets there, because he can't split a Will Call order for two tickets into two names. So, once you hear back from partiserv(AT)burningman(DOT)com (they need full name, email address, and the 8 character ticket serial codes off the back of the ticket(s) as well as the 5 digit number) that the tickets are at least real, and have satisfied yourself--through whatever means--that you are talking to the owner, it seems like you would still have to rely on him to change the name on the second ticket when he gets there.
It is possible to switch names on your will call order, but the order can only be switched to ONE name. You cannot split up an order into multiple names. If you need to give your tickets to multiple people, we suggest you have the name changed to the person who is arriving first and it will be that person's responsibility to place the other ticket(s) under the other names. This can get messy so you need to be sure you can trust the person who is picking up the tickets first. VERY IMPORTANT: When leaving tickets for people at the box office, names cannot be nicknames or incomplete names, they must be in our computer system under first and last name as seen on the person's legal photo ID.
You would have to get creative to find a means to make that a comfortable transaction for you. I admit, it would make me nervous as well, because yeah--just getting there is pricey.