Our American Easter lilies are L. longiflorum and
all greenhouse growers give them a cold treatment before they force them. Several breeders are on their way to producing everblooming lilies (with L. longiflorum in their background), and there is no dormant period needed for them. This is different. I grew Easter lilies as a greenhouse crop decades ago, and that is the only L. longiflorum I am familiar with, since the species is not very winter hardy here.
Øystein, are you saying that
all trumpet lilies don't need a cold treatment? I'd like to read up on that, if you have a source of information at the ready.