I am not in the West, so grain of salt and all that....
In my building, every Spring when the end of layoffs are near, we have a 10 minutes early start for all bid cover guys (or unassigned or extra board, the meaning is the same, unassigned FT drivers). The driver supe passes out a sheet to every driver that shows what routes we know and which we prefer. I just bid a route, but I knew more than 3/4s the routes in my building. The routes that I did not want to do at all, I crossed off for knowledge.
On Thursdays, I would get message asking what route I wanted to do, they worked off the list and would typically send me only my top 2 or 3, rather than the whole vacation list. If there were only crappy routes for the week, I would go unassigned and work call ins for the week.
There were occasionally weeks where they wanted to train someone on a route that I knew. If there was something agreeable AND a lower person did not bump the new person wanting to learn a route, I would do it.
I was the #1 unassigned guy in my building for 5 or 6 years and I have my own bid route now and I am not really liking it. I would much rather do an 85 stop rural route than a 130 stop in town route.