I last owned property in WA in 2003. I'm fairly sure the laws governing rental properties would have changed since then.
In Queensland I'm liable for smoke detectors that stopped working because tenants had removed the batteries. Trying to fight the issue would have cost me 5x the cost of shutting up and paying up. To avoid further litigation and a possible fight with my insurers in the case of a fire... I'd jump at the offer from a third party to take over responsibility for maintaining the blasted things.
The owner's liability doesn't stop at installing smoke alarms... Despite what many might think/hope or believe. This is most likely why the firm offering frequent checks and maintenance of smoke alarms is prospering. How they offset the the issue of liability would (I guess) be the deal breaker.
HH