Maestro, The community strings are defined within each context, not in the system context. Because each context is its own totally separate virtual firewall they are monitored directly via snmp not through the system context, it doesn't work that way...
This doesn't work in multi-context mode:
plccdtfw/sec/act# more disk0:/plcfw2.cfg | i communitysnmp-server host outside 10.18.58.232 community ***** version 2csnmp-server host outside 10.16.47.244 community ***** version 2csnmp-server host outside ...