Can I specify a time a file (an ad, promo or station ID) will play?
Absolutely. MegaSeg incorporates a full Scheduler and Events features. You can create schedules (like Playlist Hot Clocks based on categories/genre) and then use the Events feature to schedule them to play at certain times. And also use the Events feature to insert promos/ids/jingles/sweepers at certain intervals (every 3 segues, every 15 minutes, 59 past the hour, Tuesdays at 10:30 PM, etc).