The OC probably could make each owner pay, but it would seem petty to me. Because it would become either owner pays directly for the detectors or owner pays the OC (by levy) who pays for the detectors.
Having the OC pay for them seems more logical. And it’s an important Essential Services measure that the whole building benefits from – not just each lot owner.
The ongoing maintenance of the lot detectors is another matter. The periodic testing (eg 6 monthly), cleaning and battery replacement should generally be the lot owner’s responsibility with the OC perhaps doing a major inspection/test every 10 years or so. The latest hard-wired detector batteries can last 10 years.