Something

[default]
exten => 99,1,goto(die_grosse_queue,s,1] ;transfer someone to 99 to start

[die_grosse_queuezentrale]
exten => s,1,answer                
exten => s,n,dial(sip/1&sip/2,20)    ;try for 20 seconds to call
exten => s,n,dial(sip/3&sip/4,20)    ;didnt answer?  try next two.
exten => s,n,wait(10)                ;didnt work again?  wait 10 seconds
exten => s,n,goto(s,1)               ;start over

;PROBLEM:  this goes on forever