Apologies for this incomplete question. I believe that the "once I have.." came from another reply to an email.
The original question I had is for essentially running PS across domain boundaries. Since I first posited the question here, I have grabbed a copy of PS in a Month of Lunches (which I am thoroughly enjoying). I'm sure the answer is there and although advised to read it sequentially, perhaps you can throw me a clue where and when to look out for the answer?
So, if you're looking to use Remoting to query across domain boundaries, grab "Secrets of PowerShell Remoting" (it's a free ebook – check the Resources menu here). It covers everything. You'd want to use the Invoke-Command cmdlet to check/modify the registry on each machine (the registry is where the machine-wide Execution Policy is stored).