The actual rate paid will be negative initially. It's a margin over EURIBOR which is currently negative, so yes, the market is paying PTSB to mind money. If the bond sells above par value it'll make funding even cheaper.
These are usually issued based on portfolio maturity models when it's not a fixed rate, so a decreasing balance over 20 years or so.
From Irish Times:
"Pricing achieved on the sale was 42 basis points higher than European inter bank interest rates, with 80 per cent of the total, or €413 million, sold at 28 basis points higher than European inter bank rates. At current rates, the majority will achieve a negative yield on investment."