Correction:
"Having said this buying a $100 AAZPB perpetual note at around $50 means effectively getting a coupon yield of 2x4.85% and the possibility of the notes being redeemed".
should be:
Having said this buying a $100 AAZPB perpetual note at around $50 means effectively getting a coupon yield of 2x(4.85%+ BSWP%) and the possibility of the notes being redeemed.