They have the little tabs that knock in that help hold them in place a co-worker says these are sufficient to mount
I think that is a heck of a chance to take as if they let go it is a real hassle to get the trim in later.
I used roofing nails along with the metal tabs that nail into the wood.Now another guy says this is not ok because they are for roofing and can`t be used as can or fixture supports.
That is crazy, you may use whatever fastener you like, there is no such item as a listed nail for fixture supports.
I have used staples, nails, drywall screws and on most of our jobs Tek screws for metal studs.