I believe that SQLPS is defaulting to a different provider than the PowerShell command line so if you change the following line:
$path = "\\Servername\SQLBackupsFromPROD"
to this:
$path = "FileSystem::\\Servername\SQLBackupsFromPROD"
then you are explicitly specifying Get-Item to retrieve from the file system.
Let me know how you get on.
Gaz
-- Stop your grinnin' and drop your linen...they're everywhere!!!