I'll start by saying I hate dealing with Telstra, but the service provided has been reliable so have not had to deal with their poor customer service much.
I believe it's a deal because for $90/m (for the first 12 months) you get unlimited NBN100, phone line and calls, a new modem with 4G cellular backup, free install, no contract and 3 months of Binge.
There are cheaper plans, but they generally don't come with a modem or have free cellular backup, or Binge for 3 months.
Short version so you don't need to go though the pain I did:
I have to move from Telstra Cable to NBN as Telstra Cable is finally getting cut off. There is an unadvertised in store special that offers $20 off per month for up to 12 months on Telstra's $110 "Premium Speed + Unlimited Data" NBN100 plan. The deal appears to be available from Company owned Telstra Stores only. There is no commitment, no connection charges, and a free modem with 4G cellular backup.
It is a current discount available to all customers moving to NBN or moving to Telstra on the $110 plan. But only available at Telstra Company stores.
I moved to Telstra Cable from ADSL a few years ago, as NBN was not available in my area and Telstra was the only option for higher speeds.
When NBN came and my neighbours jumped across to NBN they complained about NBN having continual outages and poor performance, so I stayed with Telstra, and only had one outage over the last couple of years.
Telstra Cable is now being turned off and I have no choice but to move to NBN.
I'm currently paying $89/m for unlimited uncapped Cable and home phone with calls. I'm getting between 93-110Mbps so can't complain there.
I thought I would try changing plans the least painful way by reaching out to Telstra via Social Media, but they just said the retail plans are all they can offer ($110/m).
I called Telstra to see if I could just move across to NBN without any changes and have the same speed and pay the same price. They said no problems it would only cost $1 more a month making it $90, I said ok happy to do it. But after faffing about for 30 minutes they read out the conditions and told me that was the NBN50 service. I told them that was not the same as I was already on 100+Mbps. They then said they could only do it for the retail price of $110. They suggested visiting a Telstra Shop as they can offer discounts the call centre cannot. This whole process from waiting on hold to giving up took over 1.5 hours.
I visited my local Telstra shop for the first time, they also said it shouldn't be a problem keeping everything the same, and again tried to sign me up to the NBN50 plan for $90. I again pointed out this was not the same. They then told me they are a franchise store and they do not have access to the discounts that company stores have and told me which stores nearby are company stores.
I visited one of the suggested company stores and was told there was a 4 hour wait to speak to a consultant. So left.
I visited another Telstra store today and was told the wait was 30 minutes, and they would call when someone was free. This was ok today as I had other shopping to do anyway.
When the appointment came they also offered to put me on the NBN50 plan, I again told them that was not the same. Then they told me it would be $110, I said that was too much and I'll go with mate or one of the others instead. They then looked through the list of promotions available on screen and found there was a $20 a month discount on the $110 plan for up to 12 months available. No install fee, new modem (same Gen 2 as I already have), no contract.
It really should not be this hard to retain a customer.
Edit: FTTP or HFC ONLY for new customers. YMMV for existing customers NBN100 using FTTC/FTTN