Thanks for the extra detail. I was oversimplifying which is a bad idea in these parts. The BFT going to the cabinet should have plenty of room for those extra fibres. No new spine duct construction is where I was going as all you need aside from a fibre blow is there.
You could do it with a single fibre but that involves pushing WDM into the field. The appetite for that might be limited.
There is a little WDM in the field I understand but it's pretty rare.
