Re: don't go with just one supplier
At a previous company I did that, the buildings (2 of them) were designed for multiple occupancy so each had multiple ducts.
We were on a road which had a single duct running down it - however one exchange was left out the building and the other right, so we got BT to run one cable out of the left duct and turn left, and the other out of the right duct and turn right.
Mostly resilient (I will add we had two 30way fibre cassettes coming into the building) the weak point was the single comms room but if that went down we didn't really care about the external links as we failed over to the backup site, which also had the same design. The backup site was worse due to the location but I managed to get BT to minimise the cross over for the fibres to just one junction on the road which was an acceptable risk.