Experimental, http://apple.stackexchange.com/q/52619/8546

sh-3.2$ sudo /usr/sbin/bless -mount / -firmware ~/Desktop/MBPRetinaEFIUpdate-1.3/MBP111_0138_B03_LOCKED.scap --recovery --setBoot --nextonly --verbose
EFI found at IODeviceTree:/efi
Aggregate boot path is IODeviceTree:/PCI0@0/SATA@B/PRT0@0/PMP@0/@0:4
GPT detected
Booter partition required at index 5
System partition found
Booter partition found
Preferred system partition found: disk0s1
Returning booter information dictionary:
<CFBasicHash 0x7fe7b8c0ac90 [0x7fff7d875f00]>{type = mutable dict, count = 3,
entries =>
	0 : <CFString 0x1048a5e70 [0x7fff7d875f00]>{contents = "System Partitions"} = (
    disk0s1
)
	1 : <CFString 0x1048a6650 [0x7fff7d875f00]>{contents = "Data Partitions"} = (
    disk0s4
)
	2 : <CFString 0x1048a6670 [0x7fff7d875f00]>{contents = "Auxiliary Partitions"} = (
    disk0s5
)
}

Substituting ESP disk0s1
Mounting at /Volumes/bless.Xksk
Executing "/sbin/mount"
Returned 0
Deleting contents of EFI cache directory
Creating /Volumes/bless.Xksk/EFI/APPLE/FIRMWARE if needed
Deleting previous contents of /Volumes/bless.Xksk/EFI/APPLE/FIRMWARE
Opened dest at /Volumes/bless.Xksk/EFI/APPLE/FIRMWARE//MBP111_0138_B03_LOCKED.scap for writing
preallocation not supported on this filesystem for /Volumes/bless.Xksk/EFI/APPLE/FIRMWARE//MBP111_0138_B03_LOCKED.scap

/Volumes/bless.Xksk/EFI/APPLE/FIRMWARE//MBP111_0138_B03_LOCKED.scap created successfully
Relative path of /Volumes/bless.Xksk/EFI/APPLE/FIRMWARE//MBP111_0138_B03_LOCKED.scap is \EFI\APPLE\FIRMWARE\MBP111_0138_B03_LOCKED.scap
IOMedia disk0s1 has UUID 4E600427-B0D6-45C6-987C-A97C74F2493F
Executing "/sbin/umount"
Returned 0
Write to RTC: 0
Setting EFI NVRAM:
<CFBasicHash 0x7fe7b8c0c8f0 [0x7fff7d875f00]>{type = mutable dict, count = 1,
entries =>
	2 : <CFString 0x1048a5eb0 [0x7fff7d875f00]>{contents = "efi-apple-recovery"} = <CFString 0x7fe7b8c0cbe0 [0x7fff7d875f00]>{contents = "<array><dict><key>IOMatch</key><dict><key>IOProviderClass</key><string>IOMedia</string><key>IOPropertyMatch</key><dict><key>UUID</key><string>4E600427-B0D6-45C6-987C-A97C74F2493F</string></dict></dict><key>BLLastBSDName</key><string>disk0s1</string></dict><dict><key>IOEFIDevicePathType</key><string>MediaFilePath</string><key>Path</key><string>\EFI\APPLE\FIRMWARE\MBP111_0138_B03_LOCKED.scap</string></dict></array>"}
}

sh-3.2$ clear ; diskutil mount /dev/disk0s1 ; ls -l /Volumes/EFI/EFI/APPLE/FIRMWARE/ ; diskutil unmount /dev/disk0s1





Volume EFI on /dev/disk0s1 mounted
total 16514
-rwxrwxrwx  1 gjp22  staff  8454768 31 Mar 02:55 MBP111_0138_B03_LOCKED.scap
Volume EFI on disk0s1 unmounted
sh-3.2$