Worth checking, although they normally price the one-ways high enough to discourage that.
On the back-to-back side, l guess I could also book one of the back to backs with a different (non *A) airline and UA would never know. Still leaves the moral dilemma of course.
Ah well, maybe work will just suck up the cost.
Since it seems that you are a member of UA and BA, use both those airlines.