Im an original 1950 building its unlikely the ceiling will be fire rated and the strata manager should know if its fire rated or not. You should not be made responible for making that assessment in my view.
Id be asking the SM if the building has any fire safety items or if an amnual fire safety certificate has been lodged. If not, its not fire rated.
In any case you can readily obtain fire rated covers and seals for downlights, so dont be to conerned about that.