Windfall? Not really. When would a furloughee have been recalled to UAL prior to this Transition Agreement? No one knows.
When will a furloughee now be recalled to CAL? In a few weeks.
Were the UAL furloughees shafted with the 737 fleet being parked? Yep. But were they thrown a huge bone by this guaranteed hiring arrangement? Most definitely. I'm amazed they aren't thanking the CAL/UAL transition teams profusely. The recalled folks get the best of both worlds and get to keep their original UAL seniority for the SLI. I can't find evidence of that ever being done before.