Police, fire service, and customs - They're all civil servants, and the government provides some form of housing support. The level of support depends on the civil service rank though.
My uncle is still with the HKPF, and I'm not sure about what level of housing benefits he received as a police constable because he still lived with my grandparents. When he made Probationary Inspector, he moved into government quarters... and the apartment he was assigned had to be at least 1000 sq feet. He stayed there until promotion to Senior Inspector, when he was eligible to move to larger quarters... and I swear to god that apartment was like a fucking mansion (my cousins each had a hefty bedroom and there was still space for a playroom that doubled as my grandmother's bedroom whenever she visited lol). He managed to stay there after promoting to Chief Inspector, but once he moved up to Superintendent he was required to move out - I suppose the government expects that once you've made rank you ought to earn enough or have enough saved up for a mortgage. I'm pretty sure he doesn't receive any direct housing allowance right now.
I'm not sure about commissioners though (tbf there are only 25 full time police that fall in the commissioner bracket of rank), because we've got family friends that made rank (at least in the upper brackets of rank) in the civil service and I'm pretty sure they lived in government quarters.
1000 sq feet is huge by HK standard! I suppose civil service is probably the best job in HK: the pay, the benefits and the job security.