Good analysis, Bonzo
, although I'm skeptical of the standard sci-fi convention that merely copying a brain's contents (AI or organic) and installing them in a different platform constitutes transferring or resurrecting the original identity. A consciousness isn't just data and memories, it's an active, dynamic emergent process taking place within a brain. It's as much a function of the hardware itself, its initial conditions, and its state at any given moment as it is of the data stored within it. So I don't agree with the fictional conceit that resurrecting a mind is as simple as copying a JPEG. A conscious mind is far more complex than that, so it stands to reason that the process of preserving or recreating it would also be far more complex -- and that running the same memories on a different piece of hardware would result in a distinct entity, more an offspring of the original than a direct continuation.
Granted, VGR (along with "Ship in a Bottle") has established that it's relatively easy to transfer a holographic consciousness from one storage medium to another. But, with the exception of "Living Witness," it's generally shown that not as copying the mind, but as transferring it whole so that it is removed from its original storage site at the same time it's installed in the new one. That's consistent with the idea that it's more a process than a program -- not just an inert lump of data being uploaded, but a dynamic and shifting set of activity states and interconnections that can move through a network as a coherent pattern. (Think of consciousness as analogous to a wave pattern moving through a medium. When an ocean wave moves through water, the actual water molecules don't move with it; they just oscillate up and down, but the greater pattern they form through the relationship of their individual motions is itself moving as a coherent whole.) So an AI consciousness could "move" through a network from one body or mainframe to another by altering the pattern of the network's activity; but storing the data it contained and starting it on a separate system would be a different matter.
Maybe, if you had enough storage space, then you could store a "snapshot" of the network's pattern of activity at the moment the consciousness was stored, analogous to what Windows does when you put your PC in hibernate mode (only far more complex and detailed). That way, you could use both the stored data and the snapshot of the system's state to create a closely equivalent configuration on a separate system and essentially duplicate the original consciousness. That would explain "Living Witness." But what Data downloaded into B-4 was just his memories; we have no reason to believe it contained such a finely detailed snapshot of his own brain's activity pattern. Which would mean that what Soong retreived from B-4 and downloaded into the new android body wasn't Data's identity, just his knowledge and memory. Which is why I believe that this new "Data" is more an offspring than a resurrection. He's Data Junior.