Place in remotes, when a user joins a channel it checks if auto voice for that channel is on.
on @:TEXT:!avoice*:#:{
if ($2 == on) set $($+(A-V,$chan),2) on
if ($2 == off) unset $($+(A-V,$chan),2)
}
on *:JOIN:#:{ if ( $($+(A-V,$chan),2) == on) mode $chan +v $nick
else if ( $($+(A-V,$chan),2) == $null) halt
}