i used to work at paramount studios. i worked on shows like cheers, wings, in living color, fresh prince, and arsenio hall. i don't know for sure about wb, but here's how paramount did it.
getting tickets
tickets were free. paramount did not charge. so, they were NOT a guarantee of admission. we were always very sure to make sure the ticket-holders knew that.
tickets were numbered and distributed either at the paramount gate or by some of our street guys - we usually had them at venice and hollywood blvd.
the key is to get the lowest number ticket you can.getting into the show
once you have your ticket, you go back to the studio at the appointed time and line up according to your ticket number. the lower the number, the closer you are to the front.
once the crew loads all the vip and special groups, they then count to see how many seats are left. they then fill the remaining seats with the ticket holders.
so, that (in a nutshell) is how paramount did it. again, i'm not sure about wb, but i suspect it's pretty similar. i checked the wb webpage, but couldn't find any info on how they fill the audience. but, you can try to email them via the following link:
warner bros customer service.
with friends nearing the end, i suspect it's going to be quite difficult to get in. when cheers ended, almost everyone was a vip of some sort.
good luck!
[edit] - try this contact. it has to do with studio tours, but i bet they'll be a good start.
VIP STUDIO TOURS
Danny Kahn
818.954.1008