Huh - yeah ... I suppose there is that.
Hmm - you COULD try (bit of a dirty hack, but worth checking potentially) to see whether setting POSH's run-mode to "unrestricted" before you execute this script (as an admin) might help?
I.e.: try:
Set-ExecutionPolicy unrestricted
Powershell is ... "a bit odd" at times (though I can understand why - it can give you access to a LOT of stuff to a potential bad guy, so ... ) ...
If that helps ... great.
Otherwise, yeah ... I suspect you'd need to check into what other options (if *ANY* exist) to run an elevated script without interaction.
Maybe digitally signing it might help?
Infos on how to do that (and trusted certs) can be found here -- (links to 3rd party sites):
- Signing PowerShell Scripts - Scott Hanselman
Hope that'll help.