There is at least one spawn point outside of the arena it seems.
I used the wall exploit to get outside and kill the remaining troop, all can be seen in this capture:
http://www.aventureslaurentiennes.com/video/Spawn bug.wmv
I used the wall exploit to get outside and kill the remaining troop, all can be seen in this capture:
http://www.aventureslaurentiennes.com/video/Spawn bug.wmv