In a DSL transfer scenario, the Losing Service Provider does not receive any advanced notice of the churn. A notification to the LSP is only sent upon completion of the churn. Many years ago it was my job to process all the incoming losing service provider notifications for Telecom/Spark, so I know the process well. These notifications are sent via Wireline and require an acknowledgement from the LSP.
Also worth mentioning that the copper provisioning system only allows a single service order on.
Perhaps things have changed or broken, we get zero notification of a churn and at
no point do we need to acknowledge anything.
The exception is in an abandonment scenario eg new person moves to the property and the previous occupant forgot to cancel their broadband.