If you find legacy Metasys Fire panels at a site you should seriously consider replacing this panel with current generation technology.
They probably make heavy use of the Metasys global database, communications between NCMs via the N1 bus, and could have special algorithms loaded in them to shut down air handlers, pressurize adjacent areas to a fire incident to prevent smoke damage, and reverse the fans to pull smoke out of the building after a fire incident is cleared. All of these things need to be analyzed as part of the up front integration planning. The logic in all NCMs in the building needs to be carefully analyzed and adjusted as appropriate.
These buildings can still be a very successful integration project as long as you understand up front what you are getting into and plan accordingly.