I've made a test and worked fine for me.
22-Jul 14:53 bacula-dir JobId 9: Start Backup JobId 9, Job=Backup_Wanderlei.2016-07-22_14.53.41_13
22-Jul 14:53 bacula-dir JobId 9: Using Device "FileChgr1-Dev1" to write.
24-Jul 21:09 wanderlei-fd JobId 9: shell command: run ClientRunBeforeJob "powershell.exe C:/'Program Files'/Bacula/scripts/backup.ps1 Backup_Wanderlei.2016-07-22_14.53.41_13"
24-Jul 21:09 wanderlei-fd JobId 9: Error: Runscript: ClientRunBeforeJob returned non-zero status=1. ERR=Unknown error
22-Jul 14:53 bacula-dir JobId 9: Fatal error: Bad response to ClientRunBeforeJob command: wanted 2000 OK RunBefore
, got 2905 Bad RunBeforeJob command.
22-Jul 14:53 bacula-dir JobId 9: Fatal error: Client "wanderlei-fd" RunScript failed.
22-Jul 14:53 bacula-dir JobId 9: Error: Bacula bacula-dir 7.4.0 (16Jan16):
Build OS: x86_64-unknown-linux-gnu debian 8.3
JobId: 9
Job: Backup_Wanderlei.2016-07-22_14.53.41_13
Backup Level: Full
Client: "wanderlei-fd" 7.4.0 (16Jan16) Microsoft Professional (build 9200), 64-bit,Cross-compile,Win64
FileSet: "FS_Wanderlei" 2016-07-22 14:49:18
Pool: "File" (From Job resource)
Catalog: "MyCatalog" (From Client resource)
Storage: "File1" (From Job resource)
Scheduled time: 22-Jul-2016 14:53:39
Start time: 22-Jul-2016 14:53:43
End time: 22-Jul-2016 14:53:50
Elapsed time: 7 secs
Priority: 10
FD Files Written: 0
SD Files Written: 0
FD Bytes Written: 0 (0 B)
SD Bytes Written: 0 (0 B)
Rate: 0.0 KB/s
Software Compression: None
Snapshot/VSS: yes
Encryption: no
Accurate: no
Volume name(s):
Volume Session Id: 5
Volume Session Time: 1469140419
Last Volume Bytes: 14,827,218 (14.82 MB)
Non-fatal FD errors: 2
SD Errors: 0
FD termination status: Error
SD termination status: OK
Termination: *** Backup Error ***