Verify Time Machine Encryption from the Command-Line?
If you know the UUID before you mount the disk you can use:

diskutil coreStorage list XXXXXXXX-XXXX-XXXX-XXXX-XXXXXXXXXXXX


This will give the following output.

Logical Volume Family XXXXXXXX-XXXX-XXXX-XXXX-XXXXXXXXXXXX
----------------------------------------------------------
Encryption Status:       Unlocked
Encryption Type:         AES-XTS
Conversion Status:       Complete
Conversion Direction:    -none-
Has Encrypted Extents:   Yes
Fully Secure:            Yes
Passphrase Required:     Yes


If you know the mountpoint of the disk, you can get the UUID by the following command.

diskutil info /MOUNTPOINT | grep UUID | awk '{print $3}'


And if you do not know the mountpoint you can always run

diskutil coreStorage list


A MacMini with two encrypted drives (Macintosh SSD &amp; Backup Mini) will give the following output.

CoreStorage logical volume groups (2 found)
|
+-- Logical Volume Group XXXXXXXX-XXXX-XXXX-XXXX-XXXXXXXXXXXX
|   =========================================================
|   Name:         Macintosh SSD
|   Status:       Online
|   Size:         250140434432 B (250.1 GB)
|   Free Space:   16777216 B (16.8 MB)
|   |
|   +-&lt; Physical Volume XXXXXXXX-XXXX-XXXX-XXXX-XXXXXXXXXXXX
|   |   ----------------------------------------------------
|   |   Index:    0
|   |   Disk:     disk0s2
|   |   Status:   Online
|   |   Size:     250140434432 B (250.1 GB)
|   |
|   +-&gt; Logical Volume Family XXXXXXXX-XXXX-XXXX-XXXX-XXXXXXXXXXXX
|       ----------------------------------------------------------
|       Encryption Status:       Unlocked
|       Encryption Type:         AES-XTS
|       Conversion Status:       Complete
|       Conversion Direction:    -none-
|       Has Encrypted Extents:   Yes
|       Fully Secure:            Yes
|       Passphrase Required:     Yes
|       |
|       +-&gt; Logical Volume XXXXXXXX-XXXX-XXXX-XXXX-XXXXXXXXXXXX
|           ---------------------------------------------------
|           Disk:               disk2
|           Status:             Online
|           Size (Total):       249804886016 B (249.8 GB)
|           Size (Converted):   -none-
|           Revertible:         Yes (unlock and decryption required)
|           LV Name:            Macintosh SSD
|           Volume Name:        Macintosh SSD
|           Content Hint:       Apple_HFS
|
+-- Logical Volume Group XXXXXXXX-XXXX-XXXX-XXXX-XXXXXXXXXXXX
    =========================================================
    Name:         Backup Mini
    Status:       Online
    Size:         999860912128 B (999.9 GB)
    Free Space:   0 B (0 B)
    |
    +-&lt; Physical Volume XXXXXXXX-XXXX-XXXX-XXXX-XXXXXXXXXXXX
    |   ----------------------------------------------------
    |   Index:    0
    |   Disk:     disk3s2
    |   Status:   Online
    |   Size:     999860912128 B (999.9 GB)
    |
    +-&gt; Logical Volume Family XXXXXXXX-XXXX-XXXX-XXXX-XXXXXXXXXXXX
        ----------------------------------------------------------
        Encryption Status:       Unlocked
        Encryption Type:         AES-XTS
        Conversion Status:       Complete
        Conversion Direction:    -none-
        Has Encrypted Extents:   Yes
        Fully Secure:            Yes
        Passphrase Required:     Yes
        |
        +-&gt; Logical Volume XXXXXXXX-XXXX-XXXX-XXXX-XXXXXXXXXXXX
            ---------------------------------------------------
            Disk:               disk5
            Status:             Online
            Size (Total):       999542136832 B (999.5 GB)
            Size (Converted):   -none-
            Revertible:         No
            LV Name:            Backup Mini
            Volume Name:        Backup Mini
            Content Hint:       Apple_HFS