Phoenix, this is getting complicated, isn't it? It's good you have made progress.
Going back a bit, the purpose of port-forwarding, or alternatively, modem-bridging, is to ensure that the ATA can actually hear a digital VoIP signal coming in on port 5060. Otherwise this MAY be intercepted by a router, which usually denies uninvited access from outside to devices on your network. My post was meant to enable you to check over your whole configuration. If you have lots of time you can read up the technical stuff at http://en.wikipedia.org/wiki/Session_In ... n_Protocol
Re emergency calls: these can be made on VoIP, but the police/ambulance/fire can't do a meaningful auto look up on their phone number database to locate you. VoIP phones are portable - you can carry your ATA around with you. From memory, your VoIP number is "located " in the database at Verizon's facility in Sydney. So, if you ring 000 on VoIP, you had better be in a speaking condition to say where you really are. If this isn't sufficient you will need a PSTN number, whether from Telstra or Exetel or anyone else.
As to ATAs with VoIP and PSTN in one unit: some (most) do, some don't. Jok11n knows PAP2s pretty well.