Is this in reference to a news event? Apple has people who coach law enforcement on accessing iPhones, and one of the things they do is get them to access the phone quickly before one of the security time delays set in and the phone can’t be unlocked without bypassing the hardware encryption, which is an expensive process. One of the big mistakes the FBI made in the San Bernardino case was to ignore Apple’s direction and accidentally lock themselves out.

I don’t know what the response time is for Apple to return customer records such as purchase dates, iCloud login times, etc. Again, I’m interested to know if this in reference to a particular incident.

iPhones are not really "locked" like traditional phones are when you need to submit an unlock code (essentially a password) to the modem to allow it to connect to non-whitelisted networks.

iPhone modems are unlocked by default (so a locked iPhone will still connect and get internet access just fine) but the OS will check-in with Apple and submit the first digits of the SIM's ICCID to check if it's allowed to operate with such a SIM.

I would thus expect an unlock to be immediate, unlock request sent to Apple, a row is updated in the locked devices database, and next time the phone checks in, it gets a positive response and the OS lets you proceed. Most likely it's the carrier's stupid & outdated systems that only submit unlock requests in batches every X days or so. Could even be manual with a spreadsheet being written up by a poor slave somewhere abroad.