The 2000 International Residential Code requires a fire block: "At openings around vents, pipes, and ducts at ceiling and floor level, with an approved material to resist the free passage of flame and products of combustion."
What makes a material "approved" is that it is acceptable to the building official. Some may approve mineral wool, others tightly packed fiberglass, but all inspectors will accept the listed fire caulking (when installed according to that listing).
I find it interesting that cables are not specifically listed as requiring fire blocking, but it is universally enforced as requiring fire blocking.
