I use a version of open-source Nagios called Sentinix as a monitoring system. Takes work to get it up and running, but once it's there it's awesome. Coupled with a Win32 tray utility called NTray, we get SNMP alerts by popup windows, e-mail, or text-to-cell phone.
I haven't parsed the MIB for the 8300 yet, but if it doesn't have anything to monitor trunks (as mentioned above), then maybe Avaya should make an effort to add it; since the PRI terminates directly to the card, it's not like there's a CSU/DSU or inline probe to get traps from. Do AlarmTraq and IRISnGEN monitor trunks?