Priority Talkgroups
Unfortunately, there is no way to effectively monitor a trunked system (or conventional channels for that matter) and monitor a channel for tone-outs at the same time with almost any scanner or radio. When scanning, the 396 "samples" each system for a period of time, monitoring for activity, then moves to the next system to be monitored and samples it, and so on. In order for the scanner to activate on a paging tone, the scanner has to recieve "enough" of both tones to read them. You'd constantly be missing tones, especially with Baltimore County's tones, since they're so short.
As far as having priority talkgroups, there is no way for the scanner to truely do this either. On actual system radios, the radio is always recieving a control signal, even when it's unmuted on a voice channel (in the form of sub-audible data streams), therefore it will "know" immediately when there's activity on the priority group, and switch to monitor it (also nice because it eliminates the periodic "drops" heard during conventional priority scanning when the radio samples the priority channel). WIth the previous trunktrackers, the scanner would "check" the priority talkgroup more often while scanning, and "leave" a held talkgroup to check the control channel for activity on the priority talkgroup, very ineffective because of the time consumed while the scanner "does it's thing"