"YMMV at Your Library"
I first learned about 'YMMV' from the deal sites I check out. It stands for 'Your Mileage Might Vary' aka Your Results Might Vary.
This phrase certainly holds true from the patron perspective. Yes, my branch may be a part of the same system but there are 15+ branches and each branch is run the same but yet differently. Hell, even within my branch your interaction with one coworker could be completely different if someone else had helped you.
A patron came up to the circ desk and I could tell she was pissed but not directly at me, so I didn't take offense to her huffing and slamming her books on the desk. She told me that she had called to renew her overdue items, but those items pushed her fees over the borrowing threshold so her current overdues were barring her from renewing them herself. Whoever was covering phones that hour pretty much told her, tough ish and the materials continued to accrue overdue fees. I don't always follow the rules to a T and I ended up renewing her materials and forgiving the associated late fees. The patron was in a much better mood after this and my coworker asked her what branch she called. After she told us which branch and walked off into the stack, we both started guessing which person she had to deal with. Staff talk to other branch staff a lot, so you tend to get a feel for the branch and the people that work there even if you have never been there.
The same principle can be applied to patron interactions. The poor circ manager at the first branch I worked for had 2 hit and run incidents in the parking lot. Both happened in less than 6 months. Needless to say she would always take a look at her car from the backroom window whenever she got a chance. With so many branches covering the county, each branch has completely different demographics from the next. At the second branch I worked at, I had a patron leave a note on my windshield after their young daughter opened their car door too hard and dented my door. I probably would have not noticed the dent for awhile since it was on the passenger side. The patron was completely apologetic and paid for the repairs and the rental car.