Move (not copy) files between a non-array share and user shares on the same disk

I run Sickbeard/SAB/Deluge under a Gentoo Linux VM parallel to unRAID VM (both on the same physical box under ESXi). I have an unRAID share at /mnt/user/Media which is exported via SMB. I also have a cache drive installed, with a non-array directory at /mnt/cache/.Scratch exported via SMB (smb-extra.conf).

On Gentoo, these are mounted at /mnt/tank/Media and /mnt/tank/Scratch.  Sickbeard points to a series folder at, for example, /mnt/tank/Media/video/series/Firefly; SAB and Deluge use the Scratch share as the work directory, and completed downloads are unpacked to /mnt/tank/Scratch/unsorted.

Now, when Sickbeard processes a new file like /mnt/tank/Scratch/unsorted/Firefly.S01E01/firefly.s01e01.mkv, it will move it to /mnt/tank/Media/video/series/Firefly/. Since the Media share is configured to use the cache drive (the same physical drive the non-array share is on), the end result here is that the file has effectively just been moved and renamed on the same disk (an operation that should be almost instantaneous). However, because there are several layers of abstraction from the underlying filesystem at play here, what actually occurs is that a full copy of the file is done, which can take some time for larger files.

I understand that part of this is a limitation of the SMB/CIFS protocol, as the mapped shares are not aware that the underlying filesystems are on the same disk. Would NFS do any better in this regard, or will the underlying unRAID driver also force it to do a copy in this scenario, since we're moving files in and out of the array (even though it's actually just to the unprotected cache drive, so parity does not come into play here)?

I realize I could just have SAB unpack directly to the Media share, but then I'm concerned that if the mover script fires while Sickbeard is in the middle of processing my split levels would not be honored correctly. I also want to keep my Deluge seeds out of the protected array, but still be able to process them through Sickbeard the same way.