Mass Calling, Code Red, Traffic Design?

Experiencing ever increasing mass call events that are overloading our common transport groups from the access tandem to our central office trunk groups. Offered load for this machine generated announcement calls is sometimes 4 times normal Busy Hour call volume. Anyone experiencing the same and what can a traffic engineer do in terms of augmenting trunk groups when such trunk augments would exhaust Tandem switch. Upcoming Elections will produce more call volumes and blocking will be more common.