I'm not sure what you mean the sacking has to be negotiated? In most cases the business decides(for whatever reason) that they no longer want the employee to work for them.It could be gross misconduct and instant dismissal,or a series of misdemeanours that have resulted in dismissal...If someone with a contract gets the sack, in whatever industry it's in, the terms of that sacking have to be negotiated. There's no hard and fast rule about what those terms should be.
It's different for most salaried people, in any industry, because they tend not to have contracts as such, they'll be on a months notice, 3 months, or whatever.
Very little negotiation involved,a bit of mitigation thrown over the table as a plea of mercy for the condemned individual,a 5 minute recess and the same outcome!!