I don't undertand how it can work. I assume the spam list is shared by all users, oherwise it will no be useful at all:
Let's supouse Apple is evil (or they recive an order from a judge) and they want to know who is calling 5555-1234
1) Add a new empty "spam" numbers encrypted database to the server (so there are now two encrypted databases in the system)
2) Add the encrited version of 5555-1234 to it.
3) When someone checks, reply the correct answer from the real database and also check in the second one and send the reply to the police.
> One example of how we’re using this implementation in iOS 18, is the new Live Caller ID Lookup feature, which provides caller ID and spam blocking services. Live Caller ID Lookup uses homomorphic encryption to send an encrypted query to a server that can provide information about a phone number without the server knowing the specific phone number in the request.
Privacy by design is always nice to see.