I grow some of those and they are hardy here, which gets quite cold. I obtained them from a local nursery. Since I live in a dry climate, they do well.
I've got
Delospema Beaufort West
Delosperma dyeri Red Mountain (very pretty)
Delosperma nubiginum (extremely prolific grower)
Delosperma Tiffindell (really nice!)
I think the T & M hardy mixed is a four pack of plants, which make me wonder.
