Wouldn't this do the same?

$sName = "mysvr"

$dbName = "mydb"

$server = New-Object Microsoft.SqlServer.Management.Smo.Server($sName)

$db = $server.Databases[$dbName]

Get-ChildItem $db.PrimaryFilePath -Recurse | Where-Object{($_.psiscontainer)} | Get-Acl

# ..