I alot of ISPs are not offering the use of the UniV ports on the NBN
Just like to add, the reason is primarily related to the CSG (Customer Service Guarantee) with voice services... From a lot of reading, the government have failed to update the CSG and Telecommunications Act when it revised the NBN rollout 3 yeas ago, effectively killing the CSG on voice services for the majority of NBN users. (Even with the NBN as a whole, there is no CSG for the data side of things).
As legislated, the CSG applies to all Standard Telephone Services (that is PSTN/POTS, ISDN and fibre (UNI-V port on NBN) based services), and may optionally apply to other voice services and voice delivery methods IF the service provider wishes to do so. (AFAIK not one RSP has done this, except Telstra, as they are legislated to do so under certain conditions).
In the world of NBN, most RSPs are providing voice services on the data side of things via VOIP (UNI-D port on FW/FTTH), which allows them to, via your services agreement waive any and all rights of the CSG. (Hence it's cheaper). The downside to waiving your rights, is that any service restoration is simply best-effort. (meaning whenever they feel like it)... And I personally can not find any documentation on NBN's responsibility for service restoration times, other than those referred to by the CSG if the CSG applies to your connection. (So for the majority of users, who waived their rights to the CSG, that means best-effort on the part of NBN, ergo, whenever they feel like it).
This is where things go to crap, for those on HFC, FTTN or FTTB connections, all voices services are provided on what NBN consider data-only connections, which, by law, it is entirely up to the RSP to define if the CSG applies or not for the voice component of the service. So for most people, when they sign up for NBN with their RSP, the RSP requires as part of the service agreement that they waive any and all rights of the CSG, so the customer no longer have access to the CSG, hence no responsibility on the part of the service provider to actually provide guaranteed service restoration times or compensation if the service can't be repaired within a reasonable time period. (And how long is reasonable, that's up to NBN to decide, not the RSP or the customer).
The only exception is Telstra, is that they must provide a voice connection which the CSG applies if the customer requests it. (as mentioned earlier, Telstra is required to by law - this is primarily to ensure those with disabilities and medical conditions have access to voice services in times of emergency). So how does Telstra do this for HFC/FTTN/FTTB connections, well if your voice service dies, Telstra now has the option to provide voice services by any alternate means they deem viable to them (that is viable to Telstra, not viable to the customer), which typically, is forwarding of your landline to your mobile phone... And if you don't have a mobile phone, Telstra is meant to provide one for you at their cost. And as for the actual service restoration time... well that's up to NBN, and as Telstra has provided an alternate service to meet the CSG, NBN can take as much time as they want to...
So for all the elderly/disabled out there that only have a landline (with priority assistance option) and a medical alert system that relies on that landline, I hope that they don't have to suffer too many outages...
For those outside of Oz, the customer service guarantee has only really applied for voice connections only*, but since most people kept their PSTN service when they signed up for a DSL connection, they continued to have the benefit of the CSG for the line which the DSL was provided on. (eg, if the DSL connection dies, one could simple report a voice fault on the line, and all services on that line would typically be restored in accordance with the CSG). But with the new NBN, things became a lot more complicated... and a lot of people haven't realised they no longer have the service guarantees or the compensation options that they used to have...
* Actually, in the past the CSG also applied for data services up to 9600bps (eg fax), but that was scrapped a while ago...
Disclaimer: if any of the above information is wrong, please let me know with references ideally to authoritative sources that covers the issue... But from my reading and understanding of what has been provided by the ACMA, TIO and NBN (as well as reading the legislation itself), the above is pretty accurate...