I found a few people asking this but no concrete answers:
Can I use NFC to pair my BH-505 with my Nexus S?
Short answer: no.
You have to pair the old fashioned way. But, but: once paired, wave your Nexus S over the back of the headband and the headset will turn on and connect to the last device they were connected to. Not as cool, but still ‘neat’. No-one else can turn their bluetooth headphones on with a wave of their phone.
Edit: this is true of both 2.3.2 and 2.3.3.
Further edit: the tag in the BH-505 is a NFC Forum Type 2 Tag, with 46 bytes of storage according to the NXP TagWriter app.
Even further edit: the BH-505 tag identifies as a Mifare Ultralight.