I've been using HGC BB for more than 20 years. My building (私樓) ain't got no HGC optical fibre. I'm using 100Mb VDSL2 and the lowest offer (after sending cut-form) was $69. As per the contract renewal section I got 2 options only, accept or do not accept.
Regarding the 100Mb category, optical fibre is usually cheaper (when there is promo) than VDSL2.
ps. My building has HKBN and PCCW optical fibre installation ... both are not my cup of tea. May switch to 3HK 5G home BB in the future. Btw, HGC is no longer a 3HK company, years ago!