JMO, but 12 gage steel wire is overkill to support 10 pounds, you likely rip a hole at attachment point of the thin sheet metal before you even come close to compromising the wire.
Nobody is ever very particular about supporting items in suspended ceilings around here, so I don't really know what is in any codes besides NEC. If I did work in some of the larger towns (like 10,000+ population) maybe I would run into more building code issues, for most part all I run into is state fire marshal on buildings with public access be it a small retail store, or a larger place of assembly. They generally focus more on finish ratings, and protection of egress routes, and sometimes make requirements that make absolutely no sense at all.
Had a small office building (new building) that happened to have full basement and wood framed floor over that basement. Basement was not public access area, and was just mechanical and storage area. Fire marshal wanted a one hour door on the basement stairwell, yet the underside of that wood framed wood sheathed floor was totally exposed. A fire in that basement would burn a hole in the floor long before threatening the location of that one hour door unless it started right in the stairs maybe:slaphead: I thought if he was going to require the one hour door he should have at least wanted a one hour rating on the basement ceiling as well.