I've had mixed experience. a local guy post on FB they needed a fill in. I knew the drummer from a friend and new their band played similar material than the one I was in at the time, so I volunteered. Less than a 6 hour notice. I asked for a setlist, he said we could go over it when I got there. I wasn't overly comfortable, but was trying to be helpful. I get there and about 1/3 of the list was foreign to me. They also didn't play a set order, just let the singer call them out. I talked to the guitar player and said "be sure to give me the song keys when she calls out the songs, and maybe show me your hands if there's a key change". He just kind of grunted. Throughout the night, I had to ask (over the mic) what key they were doing a song in. He purposely kept his back to me most of the night. I was not happy. All that succeeded in doing was making me look bad.
On the other hand, I've filled for other groups and even churches that always get me a list (usually noting if they do something different from the recording). It can be fun and refreshing, IF you're subbing for courteous, somewhat professional people.