Lead has a relitively low melting point, it may be on of the first things to fail in a fire. In dropped cielings I just get the cieling installer to shoot my support wires to the lid. Regular cieling, if I had not already cast in the light or support into the pour, Tap con, and if it's heavy, a lttle epoxy too. If its really heavy I break out the Hilti catolog for the under-cut anchors, and some epoxy...
http://www.us.hilti.com/holus/modules/prcat/prca_navigation.jsp?OID=-11561
