NBN Co has identified 1500 premises in the satellite and fixed wireless footprints that will have their ADSL services cut off due to a “rare circumstance” with the network’s design.

The company said the approximate figure of 1500 premises was current as of August 2017, though it did not indicate whether it expected the figure to rise as rollout volumes peak this year and next.

The disclosure of the number is an about-turn by NBN Co, which had earlier refused to reveal how many premises with existing ADSL connections would be only offered satellite services in future.

Most premises in NBN’s fixed wireless and satellite footprints will still have the option of ADSL services, as these do not have to be switched off and migrated to the NBN.

However, for the 1500 premises identified by NBN Co, they are likely to end up with only a satellite connection – with the alternative being mobile broadband from another telco, assuming they are within a coverage area.

CEO Bill Morrow told a parliamentary committee in August of a “very unique, rare circumstance” where some premises in fibre-to-the-node (FTTN) areas were on copper loops that were too long to support 25 Mbps and were, therefore, likely to get satellite.

“It meets the statement of expectation requirements and it can have 25 Mbps capability,” Morrow said.

But because they were located just outside an FTTN area, they would be unable to keep their existing ADSL connections due to the potential for them interfering with the nearby VDSL lines.

“Where a premises that is located outside the fixed line footprint is currently serviced from a pillar that is being jumpered to an NBN node… they receive fixed wireless or satellite even though they may have an existing ADSL service,” NBN Co said this week.

Morrow said that while the “majority” of the 400,000 premises in the Sky Muster footprint could “elect to stay on ADSL through the Telstra network if it’s available, these few will not be able to”.

“That's where we are looking to see if that's reasonable and fair, and what the other options are," he said.

Premises within FTTN boundaries have 18 months to switch across from their old ADSL services, which are then disconnected.

Within that 18 months there is a “co-existence period” where a mix of ADSL and VDSL services are active, but performance of the VDSL is degraded.

NBN Co has previously made it clear that a user's current connection to the internet is no indication of what they will receive under the NBN model.

This has seen many towns serviced by ADSL put into NBN's fixed wireless footprint, although the migration rules mean that ADSL remains an option for these users for as long as Telstra keeps this portion of its copper network on.