I don’t see the utility being very high.

PBXs? Surely you can get a block of numbers you’re allowed to have and use those.

After hours doctor return calls? Route the call through the physical office, or just call from a different number.

A system that’s overrun with spam is as useless as having no system at all. We got close to that with email in the late 90s and we’re getting close with phones today. Requiring some minor, inconsequential changes to how a few people use the system should be easily acceptable.