Well, first I thought the work type eg emergent work as you call it cannot change with time. It seems the better work type is breakdown as you said so.
Do you mean the repair for the breakdown will be started in 30 days or the time to start and complete the repair is 30 days?
Anyway, within the 30 days, the emergent job can be considered a backlog after it has been planned and scheduled to be ready for execution.