I'm aware of (but not familiar with):
router(config)#gw-accounting syslog
... which can be used to generate H.323 call start/stop CDRs (VoIP Call Detail Records).
or, if you were using the Authentication Proxy feature:
ip auth-proxy auth-proxy-audit
... but I'm, not aware of broad spectrum support for syslogging all Accounting records. If there is such support, I'll be interested to hear of it.