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Yes, that is the story I'm remembering. I did some digging, the link you provide was posted in 2011, but the book was originally published in 1992, which fits the timeline for when I was exposed to it. Thank you for finding that.
@Ellesedil Not seeing Batman doesn't rule him out of being there. Also ships in the hanger are not the only way to travel to and from the Watchtower; there is also the teleportation deck that could have been used... Honestly you're arguing an mute point; if any one person knows how to fire the cannon remotely it's Batman.
@Ellesedil As far as I know, It doesn't expressly show him there or not, but we can assume that if he knows which 3 people can fire it remotely, 2 of which where on the Watch Tower, and the 3rd was Lex, we can assume he was on the watch tower when it happened, and that he is one of the people who knows how to fire it remotely (it would be way out of character for him to allow someone else to know how to fire it remotely and him not know to himself).