Which trigger for new IPv6 PE addresses?

[drosophila]

I'm stuck trying to react to the WAN interface getting a new IPv6 privacy extensions address. I've found the "newwanipv6" trigger but that only triggers when the main IPv6 address / prefix has changed. It does, however, not trigger when privacy extension addresses expire / new ones are generated. I need to react to both these events. A cron job would be possible but running that every minute is both wasteful and slow to react. There must be a better way, can somebody please point me in the right direction?