Does this test command work?: (it works on my systems)
waithidden "C:\Windows\System32\WindowsPowerShell\v1.0\powershell.exe" -ExecutionPolicy Bypass -command "get-help | out-file C:\windows\temp\test_powershell.txt"
I created a task to test powershell and report the powershell major version through the exit code: http://bigfix.me/fixlet/details/5019
Related:
Powershell Help