Erlang C assumes that calls are independent and each and every one is answered per the model’s constraints: target service level, AHT etc. In case of broadcast storms and multiple alarms, which are very common in NOCs, many calls will be dismissed very quickly or possibly ignored, as they are easily traced to a common source. To plan for these using Erlang C you will need to estimate the level of redundancy in calls and the AHT of the calls that can be dismissed immediately, and adjust the Erlang C model inputs accordingly. This is somewhat similar to using Erlang C to staff foe multiple queues (e.g. skill based routing).
I hope this helps. Please let me know id this is too cryptic and youd like more detail…