The InboundCallRoute should be:
{ph,ph2,aa}
The phones will ring until aa answers the call. aa will answer the call after the delay set by:
Voice Services > Auto Attendant > Auto Attendant 1 > AnswerDelay
I don't know what the maximum setting is, but quite long I guess. Line Port > RingDelay will needs to be subtracted from the Auto Attendant AnswerDelay. For example if Line Port RingDelay is 4000 and Auto Attendant AnswerDelay is set to 10000, then the actual delay before aa answers after the phones start ringing will be 6000 (six seconds)
If the caller clears down, or does not input an option, then NumberOnNoInput will direct the call back to any number you put in that setting. The default is "0", which rings the phones connected to the OBi.