I'm using a public database in CloudKit for users to download assets, so in theory the user doesn't even need to log into iCloud. I noticed a user getting Network Unavailable errors (CKError 4) almost instantly when attempting to download from LTE/4G.
Edit: Noticed this is happening over LTE/4G only when there is no iCloud account on the device. However, this works on the same device without an iCloud account on Wifi.