Yes, the Fragment exchange was implemented just a few days ago.
I... don't think it's worth it to trade for the T2 Cores. You'd pay 18 Fragments for 3 T2 Cores, which would grant you at best 10 Fragments (Regalia + 5 Fragments).

Regalia themselves are used to buy Relic weapons. Currently, just Arthur's and Dartagnan's Wind weapons are out.