Accessing MSMQ via PowerShell

If you click up one level in the link you provided you'll see that you're looking at pre-release PowerShell 4.0 module documentation. Here's the link to the parent page.

PowerShell Community Extensions (PSCX) has some cmdlets for working with MSMQ, and it works with PowerShell 2.0, though.

The below method works in Powershell 2.0:

$query = "SELECT MessagesinQueue FROM Win32_PerfRawData_MSMQ_MSMQQueue WHERE Name = 'myPrivateQueueName'"
$wmiObject = Get-WmiObject -Query $query

You can list the queues with this query:

$query = "SELECT * FROM Win32_PerfRawData_MSMQ_MSMQQueue"

Look at the __PATH property which will end in .Name="theQueueName"