I hesitate to enter the fray over SLIs, but what the heck it's all "Pie in the Sky" anyways.
Today's SLIs are fairly simply to calculate given the propensity of the arbitrators to use the new found algorithmic tool. As such one can hazard a guess how they would approach a UAL/JBLU SLI.
Stovepiped Category and Class sorted by a percentage usage of longevity.
The end result would put the most senior JBLU pilot beneath the most junior WB captain at UAL in a Stovepiped list (which is not the same as the actual current bidding list).
Without digging into actual numbers and just going on my own guesses AND JUST FOR FUN!!! A UAL/JBLU SLI MIGHT look something like this:
pilots UAL JBLU
WB-Cap 2500 0
NB-CAP 3000 1200
WB-FO 3000 0
NB=FO 3500 1200
RJ-Cap 0 400
RJ-FO 0 400
What does that mean? It means JBLU Airbus captains fall from 2500 to 8500 seniority, Airbus FOs fall 8500 to 11500 and RJ pilots are on the bottom of the list, and I would expect a 5 year fence to be included as well. Keep in mind that within those groupings the sort is then dependent on what percentage is given to longevity. At 100% longevity the categories are sorted purely on date of hire. That would put the most senior JBLU captain pretty far down the list since they are (I think) 1999 hires and as a result would end up much closer to 6000 than 2500.
Now before anyone gets their panties in a bunch just remember this is an internet forum and we're talking about a rumor and nothing more so this is pure entertainment. Also, I want to emphasize for any JBLU pilot that might read this who doesn't fully understand what I mean by Stovepiped that the actual most senior RJ pilot will not end up on the bottom of the list because in a Stovepiped list it is assumed every pilot bids the most senior position possible which is, of course, never the case in the actual world.
My primary point is that recent SLIs have been somewhat mechanical as the "science" is sort of settled at the moment given that all 3 of the recent legacy mergers were Stovepiped Category and Class.