I believe the cores are made by Bcomp. If not Line is likely making their own version in house that will have similar properties to the Bcomp core. Here's a picture of the Bcomp flax seed and balsa core:
The light coloured wood is the balsa, the black lines are the flax seed, and the darked coloured wood is another species, probably maple or something. Because of the balsa strips being so thin while being supported by the flax seed composite and the other wood, they're far less prone to snapping and deteriorating over time. I definitely think they'll hold up over time.
From what I've heard those cores make for a very light ski, that still has a very damp feel, two things that usually don't go hand in hand. I can't remember who I talked to about these cores, but they sounded promising. I think they'll be a good fit for the Magnum Opus.
Link to Bcomp's core site:
http://www.bcomp.ch/58-0-flax-und-balsa-wood-cores.html