Hello,
In the USA;
There are local laws but NFPA is the most followed standard.
There is also a thing called 'self-insured' so a PLC can be the 'fire panel'.
There is also a thing called 'site approved' so a PLC can be the 'fire panel' and if all the field elements are approved then the site might be able to be approved.
Commercial, industrial and residential all have different codes, requirements, approvals, coverage, etc.
I know a company that uses Allen Bradley and MOST PLCs along with approved field devices to market, sell and install approved fire detection systems in the industrial arena.