1 - BAT the new phones into the system but make sure that the extensions are in a temporary partition that is inaccessible by any of your calling search spaces. The phones should have identical calling ability as the phones that they will be replacing (long distance calling, etc.)
2 - For every old phone you delete from the system when you are deploying them, move the same extension of the new phone that you put into the temporary partition in step 1 and set it to be in the corporate partition.
3 - After a doing this manually for a few phones and running tests to make sure everything is working normally, you can start deleting the old phones from the system in larger groups and moving the new correspnding phones in larger groups to match.
These are the paths to get to each CCX logs through CLI. They may be helpful if you are having issues accessing RTMT or downloading logs through it.
If you want to download them you have to prefix "file get " and you can add one of the options (re...