EB ENR 5.1 and 5.2 describe the areas pretty well, and the conditions/contacts for entry. Here's the blurb from 5.2:
In temporary reserved areas (TRA), military activities that are dangerous to civil aircraft take place at specified times. Restrictions apply to crossing civil aircraft. A cross-border area (CBA) is a TRA covering airspace of two or more adjacent states.
In temporary segregated areas (TSA), military activities that require the exclusive reservation of the area take place at specified times. These areas are not accessible to civil users during their activation