This will be the third time I'm involved in such an exercise, although the physical distance is greater than previously.
At least two other copies of the data will exist in parallel to the data set being transferred.
Taking the snapshot of the data that is to travel, and likewise restoring back at the destination happens at the fastest speeds known in the industry, everything is connected to the SAN with fiber cables supporting upwards of 100 Gb/s.
Multiple plan Bs will be in place, the exercise can be aborted at any time.
If there are complications with customs, then there's not much we can do about that.
Re physical vs. electronic transfer: We're moving out of a data center that has limited bandwidth, and we're not investing in a higher bandwidth line just before leaving the center.
Re mirror site: This is indeed what we're doing. The exercise is about establishing an initial "slave" copy, that will then be kept in sync at all times. Only later will the actual system move over. This has to do with SQL Server Always On Clustering and log-shipping.