Q: Can't format former Boot Camp partition [Thread II]

Can you post the output of diskutil list? What is the version of OS X installed? Is this Internet Recovery or Local Recovery? You also have FileVault2, which should be turned off. Do you have Bootcamp/Windows on the Mac?

Usually, BCA is used to delete Bootcamp partitions, not Disk Utility. BCA will do it correctly and put disk space back. Your encryption status of locked indicates FV2.

You can decrypt it using

diskutil cs decryptVolume

Usage:  diskutil coreStorage decryptVolume

        lvUUID|MountPoint|DiskIdentifier|DeviceNode

        [-stdinpassphrase | -passphrase passphrase]

Start a background decryption process that will convert the on-disk bytes which

back the given logical volume from encrypted back to plaintext. You must supply

a passphrase interactively or with one of the above parameters. After this

command completes, the conversion process will be ongoing; you can check

progress with `diskutil coreStorage list`. The volume must be unlocked.

 

Example: diskutil coreStorage decryptVolume

                  11111111-2222-3333-4444-555555555555

If you are booted in Recovery console, some CS verbs may not be available.

$ diskutil cs

Usage:  diskutil [quiet] coreStorage|CS <verb> <options>,

        where <verb> is as follows:

 

     list                     (Show status of CoreStorage volumes)

     info[rmation]            (Get CoreStorage information by UUID or disk)

     convert                  (Convert a volume into a CoreStorage volume)

     revert                   (Revert a CoreStorage volume to its native type)

     create                   (Create a new CoreStorage logical volume group)

     delete                   (Delete a CoreStorage logical volume group)

     createVolume             (Create a new CoreStorage logical volume)

     deleteVolume             (Delete a volume from a logical volume group)

     encryptVolume            (Encrypt a CoreStorage logical volume)

     decryptVolume            (Decrypt a CoreStorage logical volume)

     unlockVolume             (Attach/mount a locked CoreStorage logical volume)

     changeVolumePassphrase   (Change a CoreStorage logical volume's passphrase)

 

diskutil coreStorage <verb> with no options will provide help on that verb

 

$ diskutil cs decryptVolume

Usage:  diskutil coreStorage decryptVolume

        lvUUID|MountPoint|DiskIdentifier|DeviceNode

        [-stdinpassphrase | -passphrase passphrase]

Start a background decryption process that will convert the on-disk bytes which

back the given logical volume from encrypted back to plaintext. You must supply

a passphrase interactively or with one of the above parameters. After this

command completes, the conversion process will be ongoing; you can check

progress with `diskutil coreStorage list`. The volume must be unlocked.

 

Example: diskutil coreStorage decryptVolume

                  11111111-2222-3333-4444-555555555555

One option is to install OSX on an external volume - OS X: Installing OS X on an external volume - Apple Support and booting from it to erase the internal disk without using the Recovery Console.

Once you boot, the LV needs to be decrypted and then extended to cover the entire disk, and then BCA can be re-run to partition and install Windows.

After step 3, you should have a 'full' OS X installation running from the external disk, not an OS X Installer or Recovery Console. This 'full' OS X installation will give you access to additional CoreStorage functions.