In the central the 50% rule only comes into affect on a permanent change.
I think that is the same here too. I have another scenario that I had happen to me a couple of times this year.
My route was being cut sometimes on Mondays. I was always under the impression that if my route was cut I had the option to just stay home.
Well one of the routes that my stops went to was my old bid route that I ran for 10+ years.
I could easily run the combination route because I knew how to balnce the commits and tie the two routes together and anyone else who tried to run it by trace was pretty well screwed.
It didn't take management long to figure this out. They would call me and when I would say I'll just stay home today they would say " well we granted optional days to so many drivers and so and so called in sick we need you to come in or we won't have enough drivers"
What are my options when this happens? Should I say sorry not my problem.
It never got to that point but I really felt they were taking advantage of me when I was higher in seniority than all the people who had the day off.