System busy tones

Does anybody have or know of an official Motorola documentation that talks about queuing for system busies for the APX 6000? I've looked in all the manuals that we have, and what I can find online and I can't find anything on continuing to hold the ptt for queuing. I know that queuing is mentioned in the smart zone 2 books, however the way it's presented is not accepting by our local departments. Thanks in advance!