The native PowerShell script type is only available from BigFix client 10.0.4, which is also not supported on Win2008 / Win2012.
For those you’ll need to use the old method, build a PowerShell script using ‘createfile’ and execute it with ‘wait PowerShell.exe …’
The prerelease Script Builder Dashboard at New BigFix Labs Dashboards does not depend on the new 10.0.4 native script capability and should be helpful.