Routers that download customers userid & password

If you get a new router for the Post Office ISP, the first time you try to connect to the DSL service the router uses a default userid and password to establish the connection. It then downloads and stores the customer specific userid and password.

If you then download the configuration file you can retrieve the userid and password and use them in another router, as the password is not encrypted.

How universal is this methodology, and is it in any way standardized?

I have wondered if the Vodafone router works in the same way.

TR-069 is the standard used for remote management of CPE

EE router downloads username&password in a similar way, but the configs are encrypted and cannot be transferred between routers.

Thank you. It would be interesting to know how much use of TR-069 each of the ISPs make, and how much it enables them to reduce their support costs and provide a better level of service to their customers.

You'd have to talk with providers and suspect that a lot of what you seek would be considered commercially confidential