I'm not saying this solves every issue, but the article says:

    "With the device locked, users will be able to access very limited functions in their smartphones. These include emergency calls, incoming and select outgoing calls, settings, and backup and restore service."

For Enterprise Android devices (i.e., the one owned by the employer), the employers always had the option to install device management policy and disable parts of the phone based on those policies (e.h., remotely disable phone of an employee that was terminated). The other evergreen use case is for the parents to remotely disable/control/set policies for the phone for kids.

In this case, the telcos are just using the same device management policy. They can do so because they own the phone (have physical access to it and their legal contacts allow them to do it). I don't think Google did something specific here to enable this feature for telcos.

Note that the iPhones also has similar feature. So, switching is not going to help.

Something tells me they would not block the ability to call 911.

Emergency calls are allowed