i know he was doing a book signing near me last year following a speaking engagement he had and they rushed him into a room and he was standing and they were very strict with no outside items at all. There was no chance of getting him to sign anything else as I had baseballs too, but I got him on a book. There was also no posed photos but you could take a photo of him signing so I ended up getting one standing next to him as he was signing.
He was a real nice guy, but whoever ran the event held to their word and he did too with no outside items. It may depend on the lines though. If they are short, they may not be as strict and also depends on whether its just a book signing or whether he has some sort of speaking engagement first which limits his overall time.