I just took all of about 60 seconds and:

1) Linked my CO OnePass account to my AMEX Plat / MR account
2) Initiated a transfer of 40,000 points to OnePass
3) 40,000 is above my current balance, so it asked if I wanted to use points advance. Yes.
4) Click transfer and it's done.

5) Go to my CO OnePass account and there are the 40,000 miles.

6) Go to United.com/transfer my miles and initiate a transfer of these 40,000 miles to MileagePlus. My accounts matched up, so transfer again took place immediately.

This is a very nice benefit in my eyes; Too bad it goes away 9/30...

I am otp with the 1K line booking my award travel as we speak!