Many of CF's OLTs are contained in active roadside cabinets. They may also make use of BT exchange space but I have no evidence for or against that other than the presence of some BT exchange codes in their traceroutes.
From looking at rotues to and from CF subscriber IPs, and known ranges of CF OLTs/routers, it appears to me that there is a sensible degree of resilience built into their architecture. It's not uncommon to find OLTs connected via three or four paths to other OLTs (which may, admittedly, be multiple interfaces aggregated on the same physical route - but it looks like they aim for at least two physical routes from each OLT).
Their current deployment is I believe based on the Adtran TA5000 series, and given that they talk about 4000 premises per cabinet I suspect the TA5004 is frequently used, which offers 4x 10Gbps uplinks.
Routes tend to go from subscriber OLTs via a few more *acc* hops before ending up at an *agg* following which they end up in THN or LD8. I'd suspect that they do as much as possible on their own fibre or leased dark fibre from *agg* nodes to the core DCs. Leased lines may have made sense in their early MDU deployments but I doubt that is still the model.
Would be interested to know more about how they do it.