All good SLI points based on precedent. I think there are several points left out of the argument:

-New ALPA Merger policy includes longevity.
-There is still the no "windfall" aspect the arbitrator considers.

He must look at the totality of the seniority blend. This would be not just at the date of his decision but how that decision plays out over the next 30-40 years. With that in mind, he should look at the relative ages of both junior groups. I read somewhere that the average of the 2005+ CAL hires is around 30-35. Common sense tells me the 1999-2001 hires at UAL are around 40 pushing 50. Retirements numbers, without question, gives any furloughee an expectation to come back and enjoy the remaining years of their career. Many of them, I'm assuming, would expect to be in the top few percent at retirement. A simple staple of those 1400 would give the much younger CAL group a huge windfall in that they would have the top of the list in their later years but with many more of them having opportunities at higher paying widebodies much sooner than they would have otherwise expected. Something they will enjoy regardless of where the 1999-2001 UA hires are placed as they will retire 10-20 years before the CAL 2005+ hires. All this at the same time a staple will prevent, forever, the expectation those positions UAL guys would have had.

I would think the arbitrator would look at these issues that is addressed in ALPA merger policy in the two points above.

As as aside, I work for neither carrier but, at least to me, its stunningly obvious as to how all this went down. Again, my 2 cents that's worth less than that.