I've used starhub before and found many of the same things. I have a few theories about this - I believe that the transparent proxy that starhub has to use to block sites on the 'symbolic' blocklist is the cause - this seems to be a requirement for all ISPs here.
The first two addresses are probably wrong, and for starhub's proxy servers. The third one is likely the correct one. I'm getting the same addresses as you for the first two. The 58.x.x.x is the one for your modem, and is how you'd reach your network from outside, with proper port forwarding.
The 192.168.209.1 address is unusual, Its probably internal, but I've not seen any router use that range, or presumably use 192.168.209.254 for itself. It should work between computers on your own network, but not from outside.
Its clearly not CGN since the ip addresses are not in the CGN range, they're all regular IP addresses, and starhub dosen't use CGN on cable (I have no idea about fiber optic connections). Traffic outside port 80 seems unaffected - I had in the past used a ip address detection service on an alternate port, and I routinely SSH into my home server boxen from random networks.
How do you easily check?
I'm not sure about the fibre optic plans, but for the cable plans your router is the best place to start - If its connected to a modem (Starhub uses motorola surfboards for their low end cable plans), check at your router, and if its a cisco gateway (they use these for anything better than the 'basic' plan), log into that and check. I used to have a bash script that would get the contents of my old router's startup page, and scrape that to feed into a dynamic DNS script. The modem router, or anything connected directly to the modem will report the correct IP address.
I also found that this website has a test that shows your proxy address and real IP address
That said, Starhub's services can be uniquely broken at times. One of the side effects of the transparent proxy server is it renders a lot of download-locker sites unusable, since they all detect the same IP address.
I've had routing issues with a specific, entirely SFW webcomic for months, and then it would work again. They also do nx hijacking (which involves pointing invalid domains at a starhub search portal), though thats opt out.
I'd note, interestingly, the third site dosen't pick up my IPV6 address (which starhub supports).