Estou tentando executar um script do PowerShell a partir do PHP, mas parece não funciona

O script 'newEvent.ps1' cria um evento no servidor Exchang

$psPath = "powershell.exe";
$psDIR = "C:\\wamp\\www\\ant\\assets\\ps\\";
$psScript = "newEvent.ps1";
$runScript = $psDIR. $psScript;
$runCMD = $psPath." ".$runScript." 2>&1"; 

echo "\$psPath  $psPath <br>";
echo "\$psDIR  $psDIR <br>";
echo "\$psScript  $psScript <br>";
echo "\$runScript  $runScript <br>";
echo "\$runCMD   $runCMD  <br>";

exec( $runCMD,$out,$ret);

echo "<pre>";
print_r($out);
print_r($ret);
echo "</pre>";

Saídas:

$psPath powershell.exe
$psDIR C:\wamp\www\ant\assets\ps\
$psScript newEvent.ps1
$runScript C:\wamp\www\ant\assets\ps\newEvent.ps1
$runCMD powershell.exe C:\wamp\www\ant\assets\ps\newEvent.ps1 2>&1

Array
(
    [0] => File C:\wamp\www\ant\assets\ps\newEvent.ps1 cannot be loaded because the execut
    [1] => ion of scripts is disabled on this system. Please see "get-help about_signing"
    [2] => for more details.
    [3] => At line:1 char:39
    [4] => + C:\wamp\www\ant\assets\ps\newEvent.ps1 <<<<
    [5] =>     + CategoryInfo          : NotSpecified: (:) [], PSSecurityException
    [6] =>     + FullyQualifiedErrorId : RuntimeException
    [7] => 
)

Se eu correrpowershell.exe C:\wamp\www\ant\assets\ps\newEvent.ps1 na linha de comando, funciona be

Esta é a primeira vez que estou tentando algo assim. IrãSet-ExecutionPolicy RemoteSigned -Scope LocalMachine mas ainda me dá o mesmo erro. Na verdade, eu corriSet-ExecutionPolicy unristricted, mas ainda é o mesmo.