Can someone clarify this for me, please?

If you have already done a mutual trade in the past, and were forced to take a reduced seniority at the new facility, do you use that "new" seniority if you make another trade in the future, or your original "hire date" seniority once again?

I ask because I assumed you used the "new" seniority, but a friend of mine, who works in a different district, is going through this right now, and they are using his original seniority, not the adjusted one.

Is this just a "fortunate accident" that benefits him, or is this how it works?

Hired on date and seniority dates are 2 different things. Seniority in office would be what you traded into if you lost any. The lower of the 2 seniorities. I've never heard of anyone getting back their original hired on date. I've traded 2 times. Started in 93 now my(trade Seniority) is 2014