Unfortunately, BB wouldn't be able to actually hijack any sort of public notifications. There are always other ways of spreading information though; specifically, using the network or accessing character's inboxes. Perhaps even threadjacking network threads (as long as the other players are okay with it). Alarm systems would be handled through Navigation, as well as Mana. Staying in contact with her would be the ideal way to go. Otherwise, alarm systems would sound themselves if anything was damaged and/or in danger of shutting down.