From what I've read you would have to un-encrypt bitlocker, image with BESR, and then re-encrypt. I was looking into the same issue and this is the only way.
The KB below is for Lights Out but should apply to regular restores as well
http://seer.entsupport.symantec.com/docs/295126.htmDocument ID: 295126
http://support.veritas.com/docs/295126 E-Mail this document to a colleague
Unable to boot using Symantec Backup Exec System Recovery LightsOut Restore (LOR) on a bitlocked system
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Details:
Symantec Backup Exec System Recovery LightsOut Restore (LOR) lets the administrators restore a computer from a remote location. It works regardless of the state of the computer provided that its file system is intact.
If the data on a drive is secured using Microsoft BitLocker, the LightsOut Restore does not work on this drive.
Workaround:
It is not possible to recover the drive using LightsOut Restore if the system drive is configured with Bitlocker Encryption.
Turn off BitLocker Drive Encryption and perform the LightsOut Restore again:
1. Click Start, click Control Panel, click Security, and then click BitLocker Drive Encryption.
2. From the BitLocker Drive Encryption page, find the volume on which the BitLocker Drive Encryption needs to be turned off, and click Turn Off BitLocker Drive Encryption.
3. From the What level of decryption do you want dialog box, click either Disable BitLocker Drive Encryption or Decrypt the volume as needed.