On a workstation that only has SQL Server 2014 tools installed using the SQLPS powershell mudule to connect to a SQL Server 2012 instance using "cd SQLSERVER:\sql\servername" results in the following.
WARNING: Could not obtain SQL Server Service information. An attempt to connect to WMI on 'servername' failed with the following error: SQL Server WMI provider is not available on servername. --> Invalid namespace
This appears to be because the wmi provider checks for the computermanagement namespaces. it tries to connect to the namespaces root\Microsoft\sqlserver\computermanagement12, root\Microsoft\sqlserver\computermanagement10, root\Microsoft\sqlserver\computermanagement which are 2014, 2008, 2005 respectively. It does not try to connect to root\Microsoft\sqlserver\computermanagement11 which is the 2012 namespace.
If remote server was upgraded to 2012 then connections works as the root\Microsoft\sqlserver\computermanagement10 namespace still exists. If 2012 tools exist on workstation then connection works.