I have never seen a GB's apartment, in Brooklyn or otherwise (all the Brooklyn property is well over $1billion and more square footage than the Empire state building). And you are right, many of the apartments are "luxury". especially as the bought and rennovated the Sliver building and the Margart Hotel, etc. They are nice.
The more responsible Bethel elders are given nicer apartments. Apartments (once a year) are bid on, and anyone can bid but the person gets an apartment based on seniority. Seniority is based on when a person is baptized. Therefore, in rennovated buildings and such, the GB can get pretty much any apartment they want because they have been baptized the longest... and then the apartments trickle down from there. USUSALLY, because of the age and mobility issues, the rooms they select are closer to the administration (I don't know how that's going to work wherever they move), but that's a general rule, nothing more.
Also... Bethel has certain rules, like only three items are allowed on a surface, no candles, nothing hanging from the celiling etc., and many of us noticed during housekeeping duty (the first two weeks you are there) that the higher you are the less those rules apply... which... is annoying.
Now, from where you are, this may all be considered luxury, but from the States standard it's pretty normal... it's not like the old Pope's new apartment which is opulent to the point of absurdity.