Yes, you should be able to do this. I booked a flight through UR, basically a dummy flight for 1 pax. While you may need to wait 24hrs, I did not. It showed up in my AS account within a few hours. After it was shown on my AS account I canceled the flight with AS and had them credit the $ amount to MY WALLET. I was credited the entire dollar amount of the dummy ticket. So as my example...

Cost of ticket - $264
Points redeemed - 17653 (1.5 pts on URSR)
AS credit to my wallet - $264
Purchased 2 new tickets on AS website with companion code offer for - $202 There is a price difference because as I said it was a dummy flight, not the same flight. But I was able to book 2 AS tickets that would have cost $348 for only 17653 UR pts and I still have $62 in my wallet which I plan to use for a purchased 1st class upgrade. Basically I saved 5600 UR pts and got $62.

Now the UR website still shows the trip as active, but I pretty sure that doesn't matter. AS is aware of the changes and thats what counts. I'll also say that I'm sure if this is popular, and people use this work around alot....I'm guessing it'll get shut down some how. Until then I fully plan to take advantage of it : - )