OK, the table had me thrown off. I thought your notification was on the SLA (task_sla) table. You can only use fields from the table you are working on, or you can dot-walk to them if it is a reference field. The only SLA related field on the incident is sla_due, but I don't see any code that maintains this field. It may be a legacy field that predates the modern SLA mechanism that allows multiple SLAs to be run against a single task record.
