Main question: Can fibre optic cabling be laid through an existing underground lead-in pipe, that was put in under the impression it'd be taking copper? Or would a new trench need to be dug for the fibre?
Here's the existing cabling outside (nevermind the unfinished landscaping):

My story: (warning: this is possibly just a big whinge, but thought I'd share my woes, and maybe someone can give some insight, as I feel consumer fibre installation doesn't get talked about very much)
Built a new house in West Auckland last month, put copper phone jacks throughout, got the underground pipes outside put in on my property, anticipating a copper connection via Telecom.
Turns out I'm in a fibre-only subdivision. There's no copper here.
Apparently the cabinet on my street that is not in the Telecom Wholesale database.
This subdivision belongs to the Brightspark fibre scheme. I'm the first one living on this street. My subdivision developer and his engineer did not know that they agreed to having this be a fibre-only subdivision. Sigh. So of course my builder had no idea of this either.
The only available ISP currently that can service the fibre is WorldxChange (Xnet Fibre).
Prior to moving in, Vodafone (my previous ISP) reckoned they'd connect me no worries. Though I did ask Telecom at one point, and they said they weren't certain if they could connect me or not, but couldn't say why. Only after I moved in did they flat-out say they couldn't, but still wouldn't say why. Was only through asking Chorus that they suggested I try contacting WorldxChange. Nobody knew for sure. But yes, WorldxChange confirmed that they could service my house.
Now, the kicker is... My property developer is clueless. WorldxChange has no exact idea how far along the fibre is in here, as I'm the first customer for this street; we're both in the dark right now. I can't get any information out of Chorus over the phone. They couldn't even answer my main question above. They say they'll call back with answers but never do.
I'm finally getting a star wiring box (cable hub management thing with a patch panel) put in this week, with lots of RJ45 points throughout the house, as required by the fibre specifications, which I wish I had known months ago... My electrician was surprised that this was required, but somehow he managed to confirm this with Telecom (or Chorus?). I didn't bother initially with internal networking 'cause I figured I'd just get whatever ADSL is available and use my wireless router for most things, and have the phones plugged in to the copper BT jacks. But eh, wireless VoiP phones are expensive, so am getting lots of jacks installed for versatility.
So, next week, once the internal wiring is done, I plan on arranging a Chorus site visit (through WorldxChange) to hopefully lay the fibre to my house from the street. Or, I imagine they'll tell me why they can't lay it, eg need a trench, or maybe my street isn't ready, I've no idea. But at least they'll hopefully be able to tell me something, even if it costs me, because I can't seem to find out any other way. Though that's why I'm asking here, as a last resort.
Regarding the picture above:
You can see the white pipe beside my garage, with some sort of black cable looped through. The gray wire sticking out of the bricks is a Belden DataTwist 5e cable for copper connections, which I'm sure will be removed. I have no idea if the hole in the bricks will be big enough for a fibre cable. Tried asking Chorus for dimension specifications but they didn't know. ....
The green pipe on the left side of the photo with the same black looped cabling is supposed to stay underground. I assume it's sticking up so that Chorus knows it's there. I don't even know if it was put in that exact spot for a good reason, or if it just seemed like the best position at a guess.
This diagram is from one of the Chorus brochures:

What's missing in my scenario is the External Termination Point atop the white pipe. I assume Chorus installs this. Nobody on the phone seems to know. And as I have an existing underground lead-in pipe, I'm hoping Chorus can use it, but again, I've no idea.
This is so new, the lack of information around it is disheartening. Not very friendly at all for the average consumer. ADSL/copper phone lines are straight forward but this is annoying. This is probably largely my subdivision developer's fault for not understanding what they signed up to, but for me, a home owner, trying to find out information about this, it's heck.
If you've read all the above, thanks for reading. I don't expect many to have much insight to this but maybe! And for those wondering, I'm posting from a 2degrees 3G USB data stick.
And for the record, even though Brightspark is listed as being part of the Telecom Wholesale group, Telecom Wholesale knew nothing about the fibre when I tried asking them, and flogged me onto Chorus. It really is a developer's game, not a consumer's. (and when your subdivision developer is useless, good luck!)